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Review

Biochemical factors contributing to tomato fruit sugar content: a reviewDiane M. BECKLES1*, Nyan HONG1, Liliana STAMOVA2, Kietsuda LUENGWILAI1,3

* Correspondence and reprints

Received 28 March 2011Accepted 7 June 2011

Fruits, 2012, vol. 67, p. 49–64© 2012 Cirad/EDP SciencesAll rights reservedDOI: 10.1051/fruits/2011066www.fruits-journal.org

RESUMEN ESPAÑOL, p. 64

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Biochemical factors contributing to tomato fruit sugar content: a reviewAbstract — Introduction. Consumers and processors value tomatoes with high fruit sugarcontent; however, most breeding and cultural practices negatively impact this trait. Wild tomatospecies can accumulate two- to three-fold more fruit sugar than cultivars and are proving to bevaluable both as a source of high-sugar loci to broaden the genetic base of currently producedcultivars, and as research material to understand this trait. Synthesis. While cutting-edge geno-mic approaches have taught us much about fruit phenotypes, it is still important to assess fruitenzyme activities and metabolic fluxes in lines with contrasting fruit sugar accumulation. Thesemetabolic functions are closest to the ripe fruit sugar trait. In this review, we focus our attentionon the biochemical pathways, especially starch biosynthesis, that may influence tomato fruitsugars. We try where possible to put this information into a physiological context becausetogether they influence yield. We compare and contrast sugar metabolism in cultivars and wildtomato species and identify factors that may influence differences in their fruit size. Conclusion.Although difficult, we show that it is possible to develop fruit with high horticultural yield anduse the breeding line ‘Solara’ as an example. In addition, we suggest avenues of further inves-tigation to understand the regulation and control of fruit carbohydrate content.

USA / Solanum lycopersicum / fruits / sugars / carbohydrate metabolism /carbohydrate content

Facteurs biochimiques contribuant à la teneur en sucre des fruits detomate : une revue.Résumé — Introduction. Les consommateurs et les industriels apprécient les tomates avec unfort taux en sucres, mais la plupart des pratiques culturales et d’amélioration ont un impact négatifsur ce caractère. Les espèces de tomate sauvage peuvent accumuler 2 ou 3 fois plus de sucresdans le fruit que des cultivars et elles s'avèrent précieuses à la fois comme une source de locià haute teneur en sucres pour élargir la base génétique des cultivars actuellement produits, etcomme matériel de recherche pour comprendre ce caractère. Synthèse. Alors que les approchesgénomiques de pointe nous ont appris beaucoup sur le phénotype des fruits, il reste importantd'évaluer l'activité des enzymes de fruits et les flux métaboliques dans des lignées présentantdes situations contrastées d’accumulation de sucres dans les fruits. Ces fonctions métaboliquessont les plus proches du caractère de teneur en sucres dans le fruit mûr. Dans cette synthèse,nous nous sommes focalisés sur les voies biochimiques, en particulier sur la biosynthèse de l'ami-don qui peut influencer les sucres dans le fruit des tomates. Nous essayons autant que possiblede mettre cette information dans un contexte physiologique car, ensemble, ils influencent le ren-dement. Nous comparons et mettons en contraste le métabolisme des sucres dans les cultivarset les espèces sauvages de tomate et nous identifions les facteurs qui peuvent influencer desdifférences de taille des fruits. Conclusion. Bien que cela soit difficile, nous montrons qu’il estpossible de produire des fruits présentant un rendement horticole élevé et nous utilisons la lignéesélectionnée « Solara » comme exemple. En outre, nous suggérons des pistes de recherches sup-plémentaires pour comprendre la régulation et le contrôle du contenu en glucides des fruits.

États-Unis / Solanum lycopersicum / fruits / sucres / métabolisme des glucides /teneur en glucides

1 Dep. Plant Sci., Univ. Calif.,One Shields Ave., Davis,CA 95616, USA,[email protected]

2 1632 Santa Rosa St., Davis,CA 95616, USA

3 Current address:Dep. Hortic., Fac. Agric.Kamphaeng Saen, KasetsartUniv., Kamphaeng SaenCampus Kamphaeng SaenNakhon Pathom, 73140,Thailand

Fruits, vol. 67 (1) 49

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D.M. Beckles et al.

Figure 1.Changes in fruit physiology andcarbohydrate accumulationfrom anthesis to full maturity.Tomato classification asImmature, Mature Green,Breaker, Pink and Red Ripe arebased on USDA Standards [95].DPA are approximate andbased primarily on a compositeof data from S. lycopersicum L.cv. Moneymaker as describedin Kortsee et al. [58], Luengwilaiand Beckles [30], and Carrariet al. [105], and from othercultivars as described inGillapsy et al. [14] and Schafferand Petreikov [106]. Notestarch synthesis is distinct fromaccumulation.

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1. Introduction

The tomato is one of the most popular fruits,with global production estimated at~1.26 Mt per year1. Tomato fruits are anexcellent source of vitamins A, C, E and lyc-opene, which collectively may lower therisk and occurrence of some cancers [1–3]and heart disease [4–6]. Both fresh and proc-essed tomatoes are widely used in many tra-ditional and modern dishes and the zeal fora ‘perfect-tasting’ tomato has spurred socio-political advocacy for local, sustainable,organic production of heirloom varieties [7].One key component of fruit quality is totalsoluble solids (TSS). Although TSS of ripetomato fruit is a measurement of severalchemicals, it is a convenient proxy for sugarcontent [8]. Higher TSS positively influencesconsumer fruit likeability and reduces costsassociated with processing tomatoes [8].

The problem is that fruit are bred for opti-mal postharvest handling [8] but, even whentrying to genetically select for fruit withhigher total soluble solids, a loss of yieldoccurs [9]. Exacerbating this problem is thatcommercial harvesting is usually donebefore the fruit reaches full-ripe and this cutsoff the sugar supply from the fruit, leadingto a less than favourable content [8]. Onesolution to this problem is to develop higher

TSS ‘value-added’ fruit to offset any loss ofyield and to minimise the severity of theeffect on sugars by premature harvesting. Inour review we will look at the biochemicalfactors that help to determine the potentialfor high sugar accumulation.

2. Tomato fruit development

Fruit development from anthesis to full mat-uration is regulated by changes in endog-enous and external environmental signalswhose perception is relayed by hormonaland sugar signalling [10–13]. There are fiverecognisable phases [14]: anthesis, fertilisa-tion, cell division, cell expansion and ripen-ing, with some overlap between stages. Celldivision occurs in the newly-formed fruit for7–10 days [15], or in large-fruited cultivarsfor 20 days [16], after which the final fruitcell number is set. The cells then expandfrom 10–40 days post-anthesis (DPA) due tothe vacuolar storage of photosynthate andwater, leading to a more than ten-foldincrease in fruit size [14, 17]. The final stageis ripening, in which the fruit undergoes sev-eral metabolic transformations brought onby climacteric ethylene, including the rapidimport and accumulation of sugars, degra-dation of starch and synthesis of lycopeneand carotenoids, the degradation of chloro-phyll and the softening of the cell wall [18].

Tomato yield relies partly on cell divisionand partly on cell enlargement, events thatoccur in the green developing fruit, whilefruit quality parameters are determined dur-ing ripening, especially after the climactericperiod (figure 1). Early events influencingcell number and hence yield include [14]endoreduplication [19, 20], seed number [21]and hormone production, especially inseeds [17, 22–25]. The number of cells canthen subsequently influence sink strength,i.e., import of photosynthate from thesource [26].

3. Carbohydrate metabolismin developing fruit

The carbon economy of the fruit changesas the organ matures. Sucrose is the major

1 FAOSTAT, FAO, 2006.

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Tomato fruit sugar content

https://wwwDownloade

photoassimilate translocated to the fruit.The movement of this photoassimilate fromsource to sink occurs in the phloem, and isin response to a pressure gradient devel-oped from differences in the osmotic poten-tial at the site of phloem loading in thesource, and at the site of unloading at thesink. Sucrose is transported to fruit cells viathe symplast (through the plasmodesmata)or it may be metabolised in the apoplast bya cell wall invertase and the resulting hex-oses imported via hexose transporters onthe plasma membrane (figure 2). For severalyears the accepted view was that symplasticloading of sucrose predominated in youngfruit while apoplastic loading of hexoseoccurred principally during ripening [27];however, this paradigm has been ques-tioned recently and the possibility that apo-plastic loading may occur throughout fruitdevelopment has been suggested [25].Sucrose in the cytoplasm is metabolised intoUDPglucose and fructose by sucrose syn-thase (Susy) or into fructose and glucose bythe neutral cytoplasmic invertase (figure 2).The activity of Susy, along with the hexoki-nases, may mobilise carbon from sucrose forthe hexose phosphate pool, while sucrosemetabolised by invertases may be destinedfor storage in the vacuole [27, 28], requiringactive transport into that organelle [29]. Bio-chemical and molecular evidence suggeststhat both Susy and invertase activities aredeterminants of fruit sink strength [25].

In green fruit, hexose phosphates aremostly used for the synthesis of starch,which occurs rapidly from anthesis until13 days post-anthesis (DPA) [30, 31](figures 1, 2). This period also coincideswith high levels of mitotic activity and thedetermination of the final cell number in thefruit [14, 32]. Fixing these newly importedsugars as starch may steepen the sugar gra-dient to the fruit and aid continued sugarimport [30, 33–35]. On a per fruit basis,starch reaches maximal accumulation at~40 DPA and is thereafter degraded in con-cert with ripening [30].

The starch and sucrose pools are turnedover in tomato fruit. Sucrose re-synthesismay occur via Sucrose Phosphate Synthase(SPS) and Susy, and the activity of theseenzymes remains relatively high during fruit

development [28, 36]. The enzyme isoformsinvolved in the disassembly of starch duringturnover are not known [27, 37]. Enzymescapable of degrading starch via amylolyticroutes have been detected in the plastids of

Figure 2.Carbohydrate metabolism in developing tomato fruitdirectly via the symplast or may be inverted in the apthen imported into the cell. Both sucrose and hexosesThe flux of sucrose to starch occurs early in fruit deve25 days post-anthesis (DPA). Here, sucrose metabolhexokinases dominates. Hexose phosphate intermedthe plastid for the synthesis of starch. As the fruit ripactivity declines relative to invertase and the apoplasmore significant with storage of sugars in the vacuolminimal and active degradation of the starch occurscontent available for storage.

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. Sucrose may be importedoplast to hexoses which aremay be stored in the vacuole.

lopment from anthesis to ~20–ism via sucrose synthase andiates are then imported into

ens, Susy and hexokinasetic import of hexose becomese. Starch biosynthesis is, which may add to the sugar

) 51s of use, available at




52

D.M. Beckles et al.


developing tomato fruit as early as 10 DPA,but they have not yet been shown to bedirectly involved in starch breakdown [38,39]. Substrate cycles of sucrose and starchmay provide metabolic flexibility and helpto maintain the fruit as a carbon sink [30].

4. Carbohydrate pathwaysin wild tomato fruit

It is perhaps ironic that one of the traits mostsought after during the domestication oftomato was increased yield [40], which co-incidentally led to lower fruit TSS [21]. How-ever, genetic, molecular and biochemicalcharacterisation of wild tomato species withhigh fruit TSS (10–15% compared with 4–6%in cultivars) have vastly improved ourunderstanding of carbohydrate metabolismin tomato, and can be exploited in breedingprogrammes [41]. Even among landraces ofSolanum lycopersicum L. there is a greatdeal of underutilised potential for newsources of high TSS [42–44].

Differences exist in the pathway steps(figure 2) that partially explain the distinctsugar profiles of wild and modern tomatoes

(table I). No single mechanism universallyexplains increased TSS across all of the spe-cies examined. However, in addition to met-abolic alterations, increased import ofsugars, especially during the later stages offruit development, has been identified inS. cheesmanii [45], S. chmielewskii [35, 46]S. pennellii [47], S. habrochaites [48],S. peruvianum [49] and S. pimpinellifoliumas a contributory factor [45]. And althoughsome “key” enzymes vary several-fold inactivity between cultivars and the wild rel-atives, there may also be subtle but wide-spread variation in many fruit enzymeactivities throughout development [28].

Two biochemical modifications related todifferences in sugar import during fruitdevelopment in wild tomato species havebeen identified; changes in invertase activityand changes in starch accumulation. Themagnitude and direction of the changes varyfrom species to species.

Solanum chmielewskii, S. peruvianum,S. neorickii and S. habrochaites are sucrose-storers. All except S. neorickii (where it hasnot been studied) contain invertases lessadept at converting sucrose into hexoses,which leads to high accumulation of theformer during late fruit development [25, 35,

olids traits in wild tomato species.

Locus Primary storagesugar(s)

Mechanism reported1 Reference

– fructose, glucose Increased sugar import during ripening Balibrea et al. [45]

– fructose, glucose Increased invertase activity Husain et al. [52, 53]

Lin5 fructose, glucose Apoplastic invertase with altered activity Fridman et al. [50]

sucr sucrose Reduced fruit acid invertase activity Chetelat et al. [96]

Agp-L1 sucrose Agp2 and increased fruit starch Petreikov et al. [33]

fgr, frk higherfructose:glucose

Epistatic interaction between frk3 and fgr Levin et al. [97]

– sucrose Unknown Schauer et al. [56]

– sucrose Higher sucrose import during ripening Stommel [49]

biochemical difference is the sole cause for changes in total soluble solids.

sphorylase.

Table I.Sources of high soluble s

Wild species ofSolanum

Fruitcolour

S. cheesmanii yellow

S. pimpinellifolium red

S. pennelli green

S. chmielewskii green

S. habrochaites green

S. habrochaites green

S. neorickii green

S. peruvianum green

1 This does not imply that the2 Agp is ADPglucose pyropho3 Frk is fructokinase.

Fruits, vol. 67 (1)







46, 50]. Rapid rates of sucrose recycling mayalso accelerate sucrose import in S. habro-chaites [27]. Miron et al. found, in additionto lower invertase, higher activity of Susyand SPS. They proposed that this couldamplify the sucrose gradient to fruit; sucrosewould be metabolised by Susy in the cytosolwith subsequent re-synthesis by SPS andimport into the vacuole at greater rates thanin the cultivar [48]. This is an attractivehypothesis and comports well with the ideathat sucrose is turned over in fruit and withthe higher SPS activity found in anothersucrose-storer, S. peruvianum. However, inS. chmielewskii SPS and Susy activities sim-ilar to domesticated tomatoes were meas-ured [51], suggesting that higher sucrosecycling may not occur in all sucrose-storers.There are no reports of these enzyme activ-ities in S. neorickii.

In contrast to the sucrose-accumulatingspecies, S. cheesmanii [45], S. pennellii [47,50] and S. pimpinellifolium [52] store largeamounts of glucose and fructose that maybe conditioned by higher invertase activitycompared with the cutivars. Solanum pen-nellii has been extensively studied. Highapoplastic invertase activity was found inthe columella which increased during rip-ening. This activity would magnify thesucrose gradient between the phloem andfruit parenchymal cells by the rapid inver-sion of sucrose to hexose [52, 53]. A similarmechanism may operate in S. pimpinellifo-lium in the apoplast to aid sink strength, butthere must be other factors contributing tohigh TSS in this species. About 90% of theinvertase activity in this species is vacuolar,not apoplastic, and vacuolar activity corre-lated with the linear accumulation of hexoseduring ripening [52, 53]. The situation iseven less clear for S. cheesmanii. Only thecytosolic invertase activity was higher, andslightly so, when compared with the culti-var, and only at 20 DPA when sugar importfor storage is minimal [45]. Also of note isthat although S. habrochaites stores sucrose,it has a higher ratio of fructose to glucose.This is due to the presence of the frg alleleand its epistatic interaction with fructoki-nase [54, 55]. This is desirable because fruc-tose, along with sucrose, is sweeter thanglucose [8], and attempts to engineer high

fructose by changing fructokinase activityhave been unsuccessful.

Many high-TSS wild tomatoes also showalterations in starch metabolism. Solanumchmielewskii [56], S. pennellii [28, 47] andS. habrochaites (formerly Lycopersicon hir-sutum) [57] accumulate more starch, whileS. peruvianum accumulates less starch atsome stages [58] compared with S. lycoper-sicum. The mechanism by which alteredstarch accumulates in some wild species isnot widely known except for S. habro-chaites. This species harbours a modifiedallele of the large subunit of ADPglucosepyrophosphorylase (AGPase; figure 2) whichis a key enzyme of starch biosynthesis. TheS. habrochaites AGPase remains active foran extended period, leading to higher levelsof starch biosynthesis in the fruit [33, 58].Petreikov et al. proposed that this modifica-tion simultaneously enhances sink capacity,thereby leading to higher sugar accumula-tion, and the ‘extra’ starch adds more sugarsto the final reserves in ripe fruit [33, 59]. Itmay not be surprising that some ‘sucrose-storers’ would synthesise more starch sinceit has been posited that the amount of starchsynthesised in fruit is driven by sucrose con-tent [27, 37]. Schauer et al. also suggestedthat since many of these fruit remain green,photosynthetic activity may also contributeto starch [56].

Finally, a major caveat in making cross-comparisons of fruit metabolism betweenstudies as we have done is the potential fordrawing inaccurate conclusions. For exam-ple, Solanum chmielewskii was shown toaccumulate more starch than the cultivar [56]but there are two reports that this speciesaccumulates less starch [35, 45]. And, pecu-liarly, Solanum cheesmanii does not havethe large increase in invertase activityexpected of high-TSS hexose-storers. Theseobserved disparities could be due to anumber of reasons: (i) variation in the fruittissues sampled, i.e., pericarp vs. columellavs. whole fruit. Baxter et al. found higheruptake of sugars in the columella but not inthe pericarp of S. pennellii, pointing to theimportance of enzyme tissue specificity [47].Therefore, the modest levels of invertaseactivity found in S. cheesmanii may be aresult of sampling only the pericarp and not

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D.M. Beckles et al.


the columella; (ii) variation in fruit matura-tion at the time of sampling due to devel-opmental shifts between wild tomatoes andcultivars [28], and (iii) differences in theaccessions sampled. For example, someaccessions of S. pimpinellifolium haveinvertase activity similar to cultivars [52].

5. Fruit size and yield in wildtomato fruit

Wild tomato species that produce fruit withhigh TSS content are low-yielding, while theinverse is true for cultivars. This link will beimportant to break if the tomato industrywishes to meet its goal of increasing TSSin large-fruited cultivars. Three mechanismscan be put forth to explain this. First, inlarge-fruited cultivars there could be “dilu-tion effects” [45, 60]. Hexoses have a higherosmolarity compared with sucrose whichwould lead to a greater influx of water tothe cells and, consequently, larger cell vol-umes and fruit sizes [46]. Second, sequencepolymorphisms in the fw2.2 allele canaccount for 30% of the difference in fruit sizebetween wild species and cultivars by alter-ing cell division in the pre-anthesis ovary[40]. Third, the relative proportion of hexoseto sucrose in fruit may differ between wildand cultivated types during cell division,directly affecting this process. In Arabidop-sis and legume seeds a high hexose-to-sucrose ratio at cell division stimulatesmitotic activity, leading to more cells and alarger organ [61–63]. If this phenomenon isuniversal then it may be part of the reasonfor differences in fruit size among tomatospecies. When the fruit sugar profiles ofS. lycopersicum were compared with thoseof the small-fruited S. chmielewskii [46],S. habrochaites and S. peruvianum [58], thehexose-to-sucrose ratio during cell divisionwas significantly higher in the former, sug-gesting that this could contribute to the dif-ferences in fruit size between these twospecies. This thesis requires further testingon a broader spectrum of tomato species.Also interesting would be to establish iffw2.2, which is regulated by sugars [10],

shows a differential response to hexose vs.sucrose.

6. Developing tomato lines withhigh total soluble solids contentand good yield – Solara: A casestudy

Fruit with modest increases in TSS but withno yield penalty have been producedthrough crosses involving S. chmielewskii[64] and S. pennellii [65] (TSS increases of10–12% and 6%, respectively) and, morerecently, yield increases were introducedinto a tomato variety with no concomitantchange in TSS [66]. However, engineeringhigh horticultural yield is difficult due to theconstraints imposed by source-sink rela-tions. We studied ‘Solara’, a breeding linewith fruit that are twenty-fold larger thanthose of S. pimpinellifolium L., from whichit was derived, and yet are high in TSS (9–11%), and that appears to be an exceptionto this general rule [67].

‘Solara’ was derived by crossing a Bulgar-ian cultivar (Solanum lycopersicum L.) andS. pimpinellifolium L., followed by 10 yearsof selections among the segregating popu-lation. In the experiment described (table II),‘Solara’ had a 30% higher horticultural yieldcompared with Solanum lycopersicum L. cv.Moneymaker. The fruit have high TSS from9–11% (table II), lower than that of cherrytomato hybrids (10–15%) and the S. pimp-inellifolium parent (12%; [68, 69]), buthigher than most table or processing varie-ties (4–6%; [35]). In addition, summer field-grown ‘Solara’ fruits’ TSS approaches 10–13% (L. Stamova, unpubl. data) in multipletests. ‘Solara’ fruits’ Total Sweetness Index(TSI) of 6.7 ± 0.2 (table II) is higher thanthe normal range of 3.8 to 5.0 reported forfresh market tomato varieties, indicatingan exceptionally sweet fruit [70]. The fruithas 2–3 locules and a low proportion ofgelatinous tissue which may further contrib-ute to its high [TSS / TA] ratio [71]. Whengrown under suboptimal conditions (Winter,table II), ‘Solara’ fruits' TSS were unchanged(9%), suggesting a strong genetic basis forthis trait.

Fruits, vol. 67 (1)






Fruits, vol. 67 (1

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D.M. Beckles et al.


Biochemical and physiological analysisof ‘Solara’ points to high import of sugars(primarily glucose and fructose) over alonger period compared with Moneymaker[67]. Sucrose is synthesised at high rates butaccumulation, while higher than in Money-maker, does not match synthesis, indicatinghigher rates of cycling [67]. Starch turnoverat the red ripe phase was detected in ‘Solara’but not in Moneymaker by 14C-glucosepulse-chase experiments (unpubl. data).

7. Understanding the roleof fruit metabolismin determining fruitsugar content

There are several basic questions regardingtomato fruit carbohydrate metabolism thatremain unanswered. Transgenic alterations,and repression or overexpression of variousgenes have provided some valuable infor-

mation on the roles of various enzymes infruit metabolism (table III; [72]). We agreewith others that knowledge of metabolicfluxes and enzyme activity will be importantin putting the puzzle together, and that thiscannot be overstated [28, 73, 74]. There areareas ‘ripe’ for investigation into tomato fruitcarbon fluxes that we still need to under-stand.

1. Susy, SPS and AGPase [27] are highly reg-ulated enzymes that may be constrained byregulatory loops [73, 75]. Expression ofenzymes modified by site-directed muta-genesis may promote increased fluxthrough the pathway at these points. Forinstance, changes in the activation state ofAGPase lead to more starch and higher TSS(see point 7).

2. Many fruit enzymes involved in carbohy-drate metabolism have multiple isoforms,each with unique kinetic properties andrestricted spatio-temporal occurrence (e.g.,invertases, Susy, fructokinase). Sequentialand combinatorial “knocking out” of the

es in tomato fruit derived from transgenic manipulation.

nipulation1 Fruit phenotype Reference

Ai2, CaMV3 ↑sucrose, ↓ hexose, reduced fertility, fruit set and fruit size Zanor et al. [25]

ense2, CaMV ↑ sucrose, ↓ hexoses and fruit size Ohyama et al. [24];Klann et al. [17]

ense, CaMV ↓ sucrose unloading at 7 days after anthesis, ↓ fruit set D'Aoust et al. [101]

ense, 2A116 No detectable change in starch or sucrose levels Chengappa et al. [102]

opic AtHK7,CaMV

↓ fruit size, seed dry weight, starch content, total soluble solidsat breaker stage and red ripe stage

Menu et al. [22]

ense, CaMV Delayed flowering, ↑ fruit sucrose Odanaka et al. [23]

ense, CaMV ↓ seed number, flower and fruit set, ↑ fruit sucrose Odanaka et al. [23]

sense, 2A11 ↓ fruit weight, seed number, ↑ sucrose Amemiya et al. [103]

gene promoter used.

s are used to repress gene expression.

gene promoter.

r acid invertase.

ren et al. [104].

ato (“2A11”) promoter.

rabidopsis hexokinase 1.

Table III.Role of carbohydrate gen

Enzyme Ma

Apoplastic invertase RN

Acid invertase4 Antis

Sucrose synthase 15 Antis

Sucrose synthase 15 Antis

Hexokinase 1 Ect

Fructokinase 1 Antis

Fructokinase 2 Antis

Vacuolar H+-ATPase Anti

1 Transgenic manipulation and2 RNAi and antisense method3 Cauliflower Mosaic Virus 35S4 Both apoplastic and vacuola5 Isoform designation from Go6 Fruit-specific gene from tom7 Ectopic overexpression of A

Fruits, vol. 67 (1)







various isoforms as demonstrated by Barrattet al. [76] would contribute to our basicknowledge of their unique and shared con-tributions to total enzymatic activity.

3. Membrane transporters are the gatewaysfor the movement of metabolites and com-pounds between compartments [77] andthey can have all-encompassing effects onfluxes. But the roles of several of these trans-porters remain under-studied in tomato fruit(figure 2). There is now evidence for theregulation of plant sugar transporters byendogenous sugar levels via kinases [78]which adds an interesting layer of complex-ity to delineating their role in carbohydrateaccumulation in the fruit.

4. The subcellular concentrations of metab-olites and sugars should be estimated inorder to determine potential changes inenzyme activity during development [79].For example, Susy and fructokinase areinhibited by physiological levels of fructose[80]. Knowing the concentration of fructosein the cytosol may refine our view of howthis enzyme works during fruit develop-ment.

5. Sugar signalling and sensing by invertase,hexokinases and as yet unidentified pro-teins should also be investigated. Invertasesconvert sucrose into hexoses, which in turnare used for carbon, energy and as signallingmolecules and, by inference, are implicatedin regulating all aspects of growth anddevelopment, including carbon partitioningto sinks [76, 81, 82]. The expression of eachfruit invertase isoform – apoplastic, cyto-plasmic and vacuolar – should be repressedindividually and in combination. Zanor et al.used RNAi to silence LIN5, the apoplasticinvertase in S. lycopersicum. Altered LIN5 isthe basis for high TSS in S. pennellii. In sodoing, they uncovered a web of intercon-nections between sugar content, and fruitdevelopment, fertility and importantly reg-ulation of hormonal levels [25]. Hexokinasesare sugar sensors and are central to sugarsignalling in plants [83, 84]. Overexpressionof Arabidopsis HK1 was performed using aconstitutive promoter, which led to manydevelopmental effects [22, 85, 86]. The con-sequence of overexpressing the native HKby using a fruit-specific promoter shouldalso be pursued [17, 24].

6. Little is known about the regulation ofsubstrate cycles of sucrose and starch indeveloping tomato fruit. Starch and sucroselevels are known to vary across cultivars andspecies and it seems reasonable to expectthat these cycles may be regulated differ-ently depending on genetic background.Transgenic manipulation of the degradationreaction may be one way to increase carbo-hydrate reserves [87].

7. Starch metabolism appears to help deter-mine yield and/or TSS in some tomato cul-tivars and species. As previously mentioned,higher TSS in some wild tomatoes is asso-ciated with altered starch metabolism butnow there is evidence to support this in cul-tivars, although changes in starch are not auniversal path to high TSS. Dinar and Ste-vens made a link between young fruit starchcontent and fruit TSS and the results of othercorrelative studies support this [88, 89].

There is now evidence that starch playsa more direct role in determining TSS andyield. Two studies of transgenic lineswhereby AGPase was overexpressed andsuppressed, respectively, provided someclues. In the first study, an unregulated bac-terial AGPase was transformed into tomatoand this purportedly led to higher starch andincreased TSS [90], but this report is contro-versial [87]. In another study, repression ofthe tomato AGPase activity by 90% appar-ently reduced starch to 25% of the levelsfound in wild-type and led to delayed flow-ering and lower yield. Although the resultswere tantalising in suggesting a relationshipbetween starch and sink strength, as theauthors noted, they could not rule out thatthe changes were due to somaclonal varia-tion [91].

Second, it has long been observed thattomatoes subject to salt stress accumulatehigher levels of starch in green fruit, andhave elevated TSS in ripe fruit [45, 92, 93].Initially, this was explained as a function ofdilution effects, i.e., the high electrical con-ductivity meant the phloem supply to thefruit was more concentrated. Now, Yin et al.have provided direct proof that starch hasa pivotal role since changes in salinity andosmotica altered AGPase at the transcrip-tional and posttranscriptional level, respec-tively, increasing green fruit starch

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biosynthesis [93]. As explained previously,partitioning of carbon to starch may increasesink strength in green fruit and then whenit is degraded during ripening adds to thepool of sugars imported from the phloem[33, 34, 59].

Third, perhaps the best evidence for arole of starch in determining TSS in cultivarswas found in transgenic tomatoes perturbedin malate content [94]. This set up cellularredox changes which altered the activationstate of AGPase and, in turn, starch accu-mulation that was directly linked to modu-lation of fruit TSS [94]. Collectively these datapoint to an important role for starch metab-olism in determining fruit carbon fluxes.There appear to be great differences instarch metabolism among cultivars [89] andthere is evidence that granule degradationmay be highly regulated [30]. It is intriguing,the possibility that flux in and out of starchcould represent a core control point fortomato fruit metabolism.

8. Conclusion

Fruit traits are ultimately defined by a cul-mination of molecular events. With genomicresources readily accessible for tomato,comparative cross-species analyses of DNA,RNA, protein and metabolites within theSolanaceace is possible. Sugars along withhormones are powerful regulators of organgrowth, development and metabolism, andthese factors are often intertwined to deter-mine the sugar-fruit size dynamic. However,as we are finding out, enzyme activities andbiochemical flux analysis of high-TSStomato species may still be indispensable inadvancing our knowledge of the processesunderlying fruit sugar accumulation.

Acknowledgements

We thank Drs. Nadia Bertin, BelindaMartineau, and the anonymous reviewersfor their input on initial drafts of this man-uscript. We also acknowledge Emily Kwokfor help with editing. L. Stamova thanks

Mr. Chuck Rivara of the California TomatoResearch Institute for use of greenhousefacilities; K. Luengwilai thanks the Anan-damahidol Foundation for funding. DMB’swork was supported by the Hatch Project #:CA-D*-PLS-7821-H, the France BerkeleyFund and NSF-MCB-0620001.

References

[1] Giovannucci E., A review of epidemiologicstudies of tomatoes, lycopene, and prostatecancer, Exp. Biol. Med. 227 (2002) 852–859.

[2] Giovannucci E., Lycopene and prostate can-cer risk. Methodological considerations inthe epidemiologic literature, Pure Appl.Chem. 74 (2002) 1427–1434.

[3] Giovannucci E., Rimm E.B., Liu Y., StampferM.J., Willett W.C., A, prospective study oftomato products, lycopene, and prostatecancer risk, J. Natl. Cancer Inst. 94 (2002)391–398.

[4] Arab L., Steck S., Lycopene and cardiovas-cular disease, Am. J. Clin. Nutr. 71 (2000)1691–1695.

[5] Sesso H.D., Liu S.M., Gaziano J.M., BuringJ.E., Dietary lycopene, tomato-based foodproducts and cardiovascular disease inwomen, J. Nutr. 133 (2003) 2336–2341.

[6] Boffetta P., Couto E., Wichmann J., Ferrari P.,Trichopoulos D., Bueno-de-Mesquita H.B.,van Duijnhoven F.J.B., Buchner F.L., Key T.,Boeing H., Nothlings U., Linseisen J.,Gonzalez C.A., Overvad K., Nielsen M.R.S.,Tjonneland A., Olsen A., Clavel-Chapelon F.,Boutron-Ruault M.C., Morois S., Lagiou P.,Naska A., Benetou V., Kaaks R., RohrmannS., Panico S., Sieri S., Vineis P., Palli D., vanGils C.H., Peeters P.H., Lund E., Brustad M.,Engeset D., Huerta J.M., Rodriguez L.,Sanchez M.J., Dorronsoro M., Barricarte A.,Hallmans G., Johansson I., Manjer J.,Sonestedt E., Allen N.E., Bingham S., KhawK.T., Slimani N., Jenab M., Mouw T., Norat T.,Riboli E., Trichopoulou A., Fruit and vege-table intake and overall cancer risk in theEuropean Prospective Investigation IntoCancer and Nutrition (EPIC), J. Natl. CancerInst. 102 (2010) 529–537.

[7] Jordan J., The Heirloom tomato as culturalobject: investigating taste and space, Sociol.Rural. 47 (2007) 20–41.

Fruits, vol. 67 (1)







[8] Beckles D.M., Factors affecting the posthar-vest sugars and total soluble solids intomato (Solanum lycopersicum L.) fruits,Postharvest Biol. Technol. 63 (2012) 129–140.

[9] Stevens M.A., Inheritance of tomato qualitycomponents, in: J.J. (Ed.), Plant breedingreviews, AVI Publ. Co., Westport, Connecti-cut, U.S.A., 1986.

[10] Baldet P., Hernould M., Laporte F., MounetF., Just D., Mouras A., Chevalier C., RothanC., The expression of cell proliferation-rela-ted genes in early developing flowers isaffected by a fruit load reduction in tomatoplants, J. Exp. Bot. 57 (2006) 961–970.

[11] Ho L.C., Hewitt J.D., Fruit development,Chapman and Hall, N.Y., U.S.A., 1986.

[12] Mounet F., Moing A., Garcia V., Petit J.,Maucourt M., Deborde C., Bernillon S., LeGall G., Colquhoun I., Defernez M., GiraudelJ.L., Rolin D., Rothan C., Lemaire-ChamleyM., Gene and metabolite regulatory networkanalysis of early developing fruit tissueshighlights new candidate genes for thecontrol of tomato fruit composition anddevelopment, Plant Physiol. 149 (2009)1505–1528.

[13] Wang H., Schauer N., Usadel B., Frasse P.,Zouine M., Hernould M., Latche A., PechJ.C., Fernie A.R., Bouzayen M., Regulatoryfeatures underlying pollination-dependentand -independent tomato fruit set revealedby transcript and primary metabolite profi-ling, Plant Cell 21 (2009) 1428–1452.

[14] Gillaspy G., Bendavid H., Gruissem W.,Fruits – a developmental perspective, PlantCell 5 (1993) 1439–1451.

[15] Bohner J., Bangerth F., Cell number, cell sizeand hormone levels in semi-isogenicmutants of Lycopersicon pimpinellifoliumdiffering in size, Physiol. Plant. 72 (1988)316–320.

[16] Bertin N., Lecomte A., Brunel B., Fishman S.,Genard M., A model describing cell polyploi-dization in tissues of growing fruit as relatedto cessation of cell proliferation, J. Exp. Bot.58 (2007) 1903–1913.

[17] Klann E.M., Hall B., Bennett A.B., Antisenseacid invertase (TIV1) gene alters solublesugar composition and size in transgenictomato fruit, Plant Physiol. 112 (1996) 1321–1330.

[18] Carrari F., Fernie A.R., Metabolic regulationunderlying tomato fruit development, J. Exp.Bot. 57 (2006) 1883–1897.

[19] Cheniclet C., Rong W.Y., Causse M.,Frangne N., Bolling L., Carde J.-P., RenaudinJ.-P., Cell expansion and endoreduplicationshow a large genetic variability in pericarpand contribute strongly to tomato fruitgrowth, Plant Physiol. 139 (2005) 1984–1994.

[20] Chevalier C., Nafati M., Mathieu-Rivet E.,Bourdon M., Frangne N., Cheniclet C.,Renaudin J.P., Gevaudant F., Hernould M.,Elucidating the functional role of endoredu-plication in tomato fruit development, Ann.Bot. 107 (2011) 1159–1169.

[21] Prudent M., Causse M., Genard M., TripodiP., Grandillo S., Bertin N., Genetic and phy-siological analysis of tomato fruit weight andcomposition: influence of carbon availabilityon QTL detection, J. Exp. Bot. 60 (2009)923–937.

[22] Menu T., Saglio P., Granot D., Dai N.,Raymond P., Ricard B., High hexokinase acti-vity in tomato fruit perturbs carbon andenergy metabolism and reduces fruit andseed size, Plant Cell Environ. 27 (2004)89–98.

[23] Odanaka S., Bennett A.B., Kanayama Y.,Distinct physiological roles of fructokinaseisozymes revealed by gene-specific sup-pression of Frk1 and Frk2 expression intomato, Plant Physiol. 129 (2002) 1119–1126.

[24] Ohyama A., Ito H., Sato T., Nishimura S.,Imai T., Hirai M., Suppression of acid inver-tase activity by antisense RNA modifies thesugar composition of tomato fruit, Plant CellPhysiol. 36 (1995) 369–376.

[25] Zanor M.I., Osorio S., Nunes-Nesi A., CarrariF., Lohse M., Usadel B., Kuhn C., Bleiss W.,Giavalisco P., Willmitzer L., Sulpice R., ZhouY.H., Fernie A.R., RNA interference of LIN5 intomato confirms its role in controlling Brixcontent, uncovers the influence of sugars onthe levels of fruit hormones, and demons-trates the importance of sucrose cleavagefor normal fruit development and fertility,Plant Physiol. 150 (2009) 1204–1218.

[26] Nesbitt T.C., Tanksley S.D., fw2.2 directlyaffects the size of developing tomato fruit,with secondary effects on fruit number andphotosynthate distribution, Plant Physiol.127 (2001) 575–583.

Fruits, vol. 67 (1






60

D.M. Beckles et al.


[27] Nguyen-Quoc B., Foyer C.H., A role for'futile cycles' involving invertase andsucrose synthase in sucrose metabolism oftomato fruit, J. Exp. Bot. 52 (2001) 881–889.

[28] Steinhauser M.C., Steinhauser D., Koehl K.,Carrari F., Gibon Y., Fernie A.R., Stitt M.,Enzyme activity profiles during fruit develop-ment in tomato cultivars and Solanum pen-nellii, Plant Physiol.153 (2010) 80–98.

[29] Yamaki S., Metabolism and accumulation ofsugars translocated to fruit and their regula-tion, J. Jpn. Soc. Hortic. Sci. 79 (2010) 1–15.

[30] Luengwilai K., Beckles D.M., Starch granulesin tomato fruit show a complex pattern ofdegradation, J. Agric. Food Chem. 57 (2009)8480–8487.

[31] Wang F., Sanz A., Brenner M.L., Smith A.,Sucrose synthase, starch accumulation, andtomato fruit sink strength, Plant Physiol. 101(1993) 321–327.

[32] Bungerkibler S., Bangerth F., Relationshipbetween cell number, cell-size and fruit sizeof seeded fruits of tomato (Lycopersiconesculentum Mill.), and those induced parthe-nocarpically by the application of plant-growth regulators, Plant Growth Regul. 1(1983) 143–154.

[33] Petreikov M., Yeselson L., Shen S., Levin I.,Schaffer A.A., Efrati A., Bar M., Carbohy-drate balance and accumulation duringdevelopment of near-isogenic tomato linesdiffering in the AGPase-L1 allele, J. Am. Soc.Hortic. Sci. 134 (2009) 134–140.

[34] Guan H.P., Janes H.W., Light regulation ofsink metabolism in tomato fruit .1. Growthand sugar accumulation, Plant Physiol. 96(1991) 916–921.

[35] Yelle S., Hewitt J.D., Robinson N.L., DamonS., Bennett A.B., Sink metabolism in tomatofruit. 3. Analysis of carbohydrate assimilationin a wild-species, Plant Physiol. 87 (1988)737–740.

[36] Obiadalla-Ali H., Fernie A.R., LytovchenkoA., Kossmann J., Lloyd J.R., Inhibition ofchloroplastic fructose 1,6-bisphosphatase intomato fruits leads to decreased fruit size,but only small changes in carbohydratemetabolism, Planta 219 (2004) 533–540.

[37] N'tchobo H., Dali N., Nguyen-Quoc B., FoyerC.H., Yelle S., Starch synthesis in tomatoremains constant throughout fruit develop-ment and is dependent on sucrose supply

and sucrose synthase activity, J. Exp. Bot.50 (1999) 1457–1463.

[38] Robinson N.L., Hewitt J.D., Bennett A.B.,Sink metabolism in tomato fruit. 1. Develop-mental-changes in carbohydrate metaboli-zing enzymes, Plant Physiol. 87 (1988) 727–730.

[39] Beckles D.M., The subcellular location ofADPglucose pyrophosphorylase in starch-storing cells, Univ. Camb., Camb., U.K.,1998, 168 p.

[40] Cong B., Barrero L.S., Tanksley S.D., Regu-latory change in YABBY-like transcriptionfactor led to evolution of extreme fruit sizeduring tomato domestication, Nat. Genet. 40(2008) 800–804.

[41] Knapp S., Bohs L., Nee M., Spooner D.M.,Solanaceae – a model for linking genomicswith biodiversity, Comp. Funct. Genomics 5(2004) 285–291.

[42] Agong S.G., Schittenhelm S., Friedt W.,Assessment of tolerance to salt stress inKenyan tomato germplasm, Euphytica 95(1997) 57–66.

[43] Turhan A., Seniz V., Estimation of certainchemical constituents of fruits of selectedtomato genotypes grown in Turkey, Afr. J.Agric. Res. 4 (2009) 1086–1092.

[44] Turhan A., Seniz V., Kuscu H., Genotypicvariation in the response of tomato to sali-nity, Afr. J. Biotechnol. 8 (2009) 1062–1068.

[45] Balibrea M.E., Martinez-Andujar C., CuarteroJ., Bolarin M.C., Perez-Alfocea F., The highfruit soluble sugar content in wild Lycoper-sicon species and their hybrids with cultivarsdepends on sucrose import during ripeningrather than on sucrose metabolism, Funct.Plant Biol. 33 (2006) 279–288.

[46] Yelle S., Chetelat R.T., Dorais M., DevernaJ.W., Bennett A.B., Sink metabolism intomato fruit. 4. Genetic and biochemical-analysis of sucrose accumulation, Plant Phy-siol. 95 (1991) 1026–1035.

[47] Baxter C.J., Carrari F., Bauke A., Overy S.,Hill S.A., Quick P.W., Fernie A.R., SweetloveL.J., Fruit carbohydrate metabolism in anintrogression line of tomato with increasedfruit soluble solids, Plant Cell Physiol. 46(2005) 425–437.

[48] Miron D., Schaffer A.A., Sucrose phosphatesynthase, sucrose synthase, and invertaseactivities in developing fruit of Lycopersiconesculentum Mill. and the sucrose accumula-ting Lycopersicon hirsutum Humb. andBonpl., Plant Physiol 95 (1991) 623–627.

Fruits, vol. 67 (1)







[49] Stommel J.R., Enzymatic components ofsucrose accumulation in the wild tomatospecies Lycopersicon peruvianum, PlantPhysiol. 99 (1992) 324–328.

[50] Fridman E., Carrari F., Liu Y.S., Fernie A.R.,Zamir D., Zooming in on a quantitative traitfor tomato yield using interspecific introgres-sions, Science 305 (2004) 1786–1789.

[51] Klann E.M., Chetelat R.T., Bennett A.B.,Expression of acid invertase gene controlssugar composition in tomato (Lycopersicon)fruit, Plant Physiol. 103 (1993) 863–870.

[52] Husain S.E., James C., Shields R., FoyerC.H., Manipulation of fruit sugar composi-tion but not content in Lycopersicon escu-lentum fruit by introgression of an acidinvertase gene from Lycopersicon pimpinel-lifolium, New Phytol. 150 (2001) 65–72.

[53] Husain S.E., Thomas B.J., Kingston-SmithA.H., Foyer C.H., Invertase protein, but notactivity, is present throughout developmentof Lycopersicon esculentum and L. pimpi-nellifolium fruit, New Phytol. 150 (2001)73–81.

[54] Levin I., Gilboa N., Cincarevsky F., Oguz I.,Petreikov M., Yeselson Y., Shen S., Bar M.,Schaffer A.A., Epistatic interaction betweentwo unlinked loci derived from introgressionsfrom Lycopersicon hirsutum further modu-lates the fructose-to-glucose ratio in themature tomato fruit, Israel J. Plant Sci. 54(2006) 215–222.

[55] Levin I., Gilboa N., Yeselson E., Shen S.,Schaffer A.A., Fgr, a major locus that modu-lates the fructose to glucose ratio in maturetomato fruits, Theor. Appl. Genet. 100 (2000)256–262.

[56] Schauer N., Zamir D., Fernie A.R., Metabolicprofiling of leaves and fruit of wild speciestomato: a survey of the Solanum lycopersi-cum complex, J. Exp. Bot. 56 (2005) 297–307.

[57] Schaffer A.A., Levin I., Oguz I., Petreikov M.,Cincarevsky F., Yeselson Y., Shen S., GilboaN., Bar M., ADPglucose pyrophosphorylaseactivity and starch accumulation in immaturetomato fruit: the effect of a Lycopersicon hir-sutum-derived introgression encoding forthe large subunit, Plant Sci. 152 (2000) 135–144.

[58] Kortsee A.J., Appeldoorn N.J.G., OortwijnM.E.P., Visser R.G.F., Differences in regula-tion of carbohydrate metabolism duringearly fruit development between domestica-

ted tomato and two wild relatives, Planta 226(2007) 929–939.

[59] Petreikov M., Shen S., Yeselson Y., Levin I.,Bar M., Schaffer A.A., Temporally extendedgene expression of the ADP-Glc pyrophos-phorylase large subunit (AgpL1) leads toincreased enzyme activity in developingtomato fruit, Planta 224 (2006) 1465–1479.

[60] Bertin N., Causse M., Brunel B., Tricon D.,Genard M., Identification of growth pro-cesses involved in QTLs for tomato fruit sizeand composition, J. Exp. Bot. 60 (2009) 237–248.

[61] Weber H., Heim U., Golombek S., BorisjukL., Wobus U., Assimilate uptake and theregulation of seed development, Seed Sci.Res. 8 (1998) 331–345.

[62] Weber H., Borisjuk L., Wobus U., Sugarimport and metabolism during seed deve-lopment, Trends Plant Sci. 2 (1997) 169–174.

[63] Ohto M., Fischer R.L., Goldberg R.B., Naka-mura K., Harada J.J., Control of seed massby APETALA2, Proc. Natl. Acad. Sci. U.S.A.102 (2005) 3123–3128.

[64] Yousef G.G., Juvik J.A., Evaluation of bree-ding utility of a chromosomal segment fromLycopersicon chmielewskii that enhancescultivated tomato soluble solids, Theor.Appl. Genet. 103 (2001) 1022–1027.

[65] Eshed Y., Zamir D., An introgression linepopulation of Lycopersicon pennellii in thecultivated tomato enables the identificationand fine mapping of yield-associated QTL,Genetics 141 (1995) 1147.

[66] Krieger U., Lippman Z.B., Zamir D., Theflowering gene SINGLE FLOWER TRUSSdrives heterosis for yield in tomato, Nat.Genet. 42 (2010) 459–463.

[67] Luengwilai K., Fiehn O.E., Beckles D.M.,Comparison of leaf and fruit metabolism intwo tomato (Solanum lycopersicum L.)genotypes varying in total soluble solids, J.Agric. Food Chem. 58 (2010) 11790–11800.

[68] Galiana-Balaguer L., Rosello S., Nuez F.,Characterization and selection of balancedsources of variability for breeding tomato(Lycopersicon) internal quality, Genet. Res.Crop Evol. 53 (2006) 907–923.

[69] Rick C.M., High soluble solids content inlarge-fruited tomato lines derived from a wildgreen-fruited-species, Hilgardia 42 (1974)493–510.

Fruits, vol. 67 (1






62

D.M. Beckles et al.


[70] Stevens M.A., Kader A.A., Albrightholton M.,Algazi M., Genotypic variation for flavor andcomposition in fresh market tomatoes, J.Am. Soc. Hortic. Sci. 102 (1977) 680–689.

[71] Grierson D., Kader A.A., Fruit ripening andquality, Chapman and Hall, Lond., U.K.,1986.

[72] Nookaraju A., Upadhyaya C.P., Pandey S.K.,Young K.E., Hong S.J., Park S.K., Park S.W.,Molecular approaches for enhancingsweetness in fruits and vegetables, Sci. Hor-tic. 127 (2010) 1–15.

[73] Stitt M., Sulpice R., Keurentjes J., Metabolicnetworks: How to identify key componentsin the regulation of metabolism and growth,Plant Physiol. 152 (2010) 428–444.

[74] Fernie A.R., Geigenberger P., Stitt M., Fluxan important, but neglected, component offunctional genomics, Curr. Opin. Plant Biol. 8(2005) 174–182.

[75] Stitt M., The first will be last and the last willbe first: non-regulated enzymes call thetune, BIOS Sci. Publ. Ltd., Oxf., U.K., 1999.

[76] Barratt D.H.P., Derbyshire P., Findlay K., PikeM., Wellner N., Lunn J., Feil R., Simpson C.,Maule A.J., Smith A.M., Normal growth ofArabidopsis requires cytosolic invertase butnot sucrose synthase, Proc. Natl. Acad. Sci.U.S.A. 106 (2009) 13124–13129.

[77] Weber A.P.M., Solute transporters asconnecting elements between cytosol andplastid stroma, Curr. Opin. Plant Biol. 7(2004) 247–253.

[78] Lecourieux F., Lecourieux D., Vignault C.,Delrot S., A sugar-inducible protein kinase,VvSK1, regulates hexose transport andsugar accumulation in grapevine cells, PlantPhysiol. 152 (2010) 1096–1106.

[79] Farre E.M., Fernie A.R., Willmitzer L., Analy-sis of subcellular metabolite levels of potatotubers (Solanum tuberosum) displaying alte-rations in cellular or extracellular sucrosemetabolism, Metabolomics 4 (2008) 161–170.

[80] Schaffer A.A., Petreikov M., Inhibition offructokinase and sucrose synthase by cyto-solic levels of fructose in young tomato fruitundergoing transient starch synthesis, Phy-siol. Plant. 101 (1997) 800–806.

[81] Roitsch T., Gonzalez M.C., Function andregulation of plant invertases: sweet sensa-tions, Trends Plant Sci. 9 (2004) 606–613.

[82] Ruan Y.L., Jin Y., Yang Y.J., Li G.J., BoyerJ.S., Sugar input, metabolism, and signalingmediated by invertase: roles in development,yield potential, and response to drought andheat, Mol. Plant 3 (2010) 942–955.

[83] Halford N.G., Purcell P.C., Hardie D.G., Ishexokinase really a sugar sensor in plants?,Trends Plant Sci. 4 (1999) 117–120.

[84] Rolland F., Baena-Gonzalez E., Sheen J.,Sugar sensing and signalling in plants:Conserved and novel mechanisms, Annu.Rev. Plant Biol. 57 (2006) 675–709.

[85] Dai N., Schaffer A., Petreikov M., Shahak Y.,Giller Y., Ratner K., Levine A., Granot D.,Overexpression of Arabidopsis hexokinasein tomato plants inhibits growth, reducesphotosynthesis, and induces rapid senes-cence, Plant Cell 11 (1999) 1253–1266.

[86] Roessner-TunaliU.,HegemannB.,LytovchenkoA., Carrari F., Bruedigam C., Granot D., FernieA.R., Metabolic profiling of transgenic tomatoplants overexpressing hexokinase revealsthat the influence of hexose phosphorylationdiminishes during fruit development, PlantPhysiol. 133 (2003) 84–99.

[87] Smith A.M., Prospects for increasing starchand sucrose yields for bioethanol produc-tion, Plant J. 54 (2008) 546–558.

[88] Kortstee A.J., Appeldoorn N.J.G., OortwijnM.E.P., Visser R.G.F., Differences in regula-tion of carbohydrate metabolism duringearly fruit development between domestica-ted tomato and two wild relatives, Planta 226(2007) 929–939.

[89] Luengwilai K., Tananuwong K., ShoemakerC.F., Beckles D.M., Starch molecular struc-ture shows little association with fruit physio-logy and starch metabolism in tomato, J.Agric. Food Chem. 58 (2010) 1275–1282.

[90] Stark D.M., Timmerman K.P., Barry G.F.,Preiss J., Kishore G.M., Regulation of theamount of starch in plant-tissues by Adp glu-cose pyrophosphorylase, Science 258(1992) 287–292.

[91] Obiadalla-Ali H., Understanding of carbonpartitioning in tomato fruit, Max-Planck Inst.Mol. Plant Physiol., Golm, Ger., 2003.

[92] Gao Z.F., Sagi M., Lips S.H., Carbohydratemetabolism in leaves and assimilate partitio-ning in fruits of tomato (Lycopersicon escu-lentum L.) as affected by salinity, Plant Sci.135 (1998) 149–159.

Fruits, vol. 67 (1)







[93] Yin Y.G., Kobayashi Y., Sanuki A., Kondo S.,Fukuda N., Ezura H., Sugaya S., MatsukuraC., Salinity induces carbohydrate accumula-tion and sugar-regulated starch biosyntheticgenes in tomato (Solanum lycopersicum L.cv. 'Micro-Tom') fruits in an ABA- and osmo-tic stress-independent manner, J. Exp. Bot.61 (2010) 563–574.

[94] Centeno D.C., Osorioa S., Nunes-Nesi A.,Bertolo A.L.F., Carneiro R.T., Araújo W.L.,Steinhauser M.-C., Michalska J., RohrmannJ., Geigenberger P., Olivera S.N., Stitt M.,Carrari F., Rose J.K.C., Fernie A.R., Malateplays a crucial role in starch metabolism,ripening, and soluble solid content of tomatofruit and affects postharvest softening, PlantCell 23 (2011) 162–184.

[95] Anon., United States standards for grades offresh tomatoes, USDA, Wash. DC, U.S.A.,1991.

[96] Chetelat R.T., Deverna J.W., Bennett A.B.,Effects of the Lycopersicon chmielewskiisucrose accumulator gene (Sucr) on fruityield and quality parameters following intro-gression into tomato, Theor. Appl. Genet. 91(1995) 334–339.

[97] Levin I., Lalazar A., Bar M., Schaffer A.A.,Non GMO fruit factories strategies for modu-lating metabolic pathways in the tomatofruit, Ind. Crop. Prod. 20 (2004) 29–36.

[98] Clarke M., Carbohydrates, industrial, Wiley-VCH, N.Y., U.S.A., 1995.

[99] Luengwilai K., Sukjamsai K., Kader A.A.,Responses of 'Clemenules Clementine' and'W. Murcott' mandarins to low oxygenatmospheres, Postharvest Biol. Technol. 44(2007) 48–54.

[100]Luengwilai K., Beckles D.M., Climactericethylene is not required for initiating chillinginjury in tomato (Solanum lycopersicum L.),J. Stored Prod. Postharvest Res. 1 (2010) 1.

[101]D'Aoust M.A., Yelle S., Nguyen-Quoc B.,Antisense inhibition of tomato fruit sucrosesynthase decreases fruit setting and thesucrose unloading capacity of young fruit,Plant Cell 11 (1999) 2407–2418.

[102]Chengappa S., Guilleroux M., Phillips W.,Shields R., Transgenic tomato plants withdecreased sucrose synthase are unaltered instarch and sugar accumulation in the fruit,Plant Mol. Biol. 40 (1999) 213–221.

[103]Amemiya T., Kanayama Y., Yamaki S.,Yamada K., Shiratake K., Fruit-specific V-ATPase suppression in antisense-transgenictomato reduces fruit growth and seed forma-tion, Planta 223 (2006) 1272–1280.

[104]Goren S., Huber S.C., Granot D., Compari-son of a novel tomato sucrose synthase,SlSUS4, with previously described SlSUSisoforms reveals distinct sequence featuresand differential expression patterns in asso-ciation with stem maturation, Planta 223(2011) 1011–1023.

[105]Carrari F., Baxter C., Usadel B., Urbanczyk-Wochniak E., Zanor M.-I., Nunes-Nesi A.,Nikiforova V., Centeno D., Ratzka A., PaulyM., Sweetlove L.J., Fernie A.R., Integratedanalysis of metabolite and transcript levelsreveals the metabolic shifts that underlietomato fruit development and highlight regu-latory aspects of metabolic network beha-vior, Plant Physiol. 142 (2006) 1380–1396.

[106]Schaffer A.A., Petreikov M., Sucrose tostarch metabolism in tomato fruit under-going transient starch accumulation, PlantPhysiol. 113 (1997) 739–746.

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Factores bioquímicos que contribuyen al contenido de azúcar de los frutosde tomate: un repaso.

Resumen — Introducción. Los consumidores e industriales aprecian los tomates con unfuerte índice de azúcares, pero la mayoría de las prácticas relativas al cultivo y de mejora tie-nen un impacto negativo sobre este rasgo característico. Las especies de tomate salvaje pue-den acumular 2 ó 3 veces más azúcares en el fruto que los cultivares, y resultan serapreciadas como fuente de loci de alto contenido en azúcares para aumentar la base genéticade los cultivares actualmente producidos y como material de investigación para comprenderdicho rasgo característico. Síntesis. A pesar de que los acercamientos genómicos punterosnos hayan enseñado mucho sobre el fenotipo de los frutos, sigue siendo importante evaluarla actividad de las encimas de los frutos, así como los flujos metabólicos en líneas que pre-senten situaciones contrastadas de acumulación de azúcares en los frutos. Dichas funcionesmetabólicas son las que más se acercan al rasgo característico del contenido de azúcares en elfruto maduro. En esta síntesis, nos centramos en las vías bioquímicas, particularmente en labiosíntesis del almidón, que puede influenciar los azúcares en el fruto del tomate. Intenta-mos, en la medida de lo posible, situar esta información en un contexto fisiológico, ya que,conjuntamente, influencian el rendimiento. Comparamos y contrastamos el metabolismo delos azúcares en los cultivares y en las especies salvajes de tomate, e identificamos los factoresque pueden influenciar las diferencias en el tamaño de los frutos. Conclusión. A pesar de ladificultad, ilustramos la posibilidad de producir frutos que presenten un elevado rendimientoy utilizamos la línea seleccionada « Solara » como ejemplo. Además, sugerimos vías de investi-gación suplementarias para comprender la regulación y el control del contenido de glúcidosde los frutos.

EUA / Solanum lycopersicum / frutas / azucares / metabolismo de carbohidratos /contenido de carbohidratos

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