Oil in oats

-some molecular insights

(Photo Å. Grimberg)

Anders S. Carlsson, SLU

Oat has high oil content

(Liu, Journal of Food Science, 2011)

(Photo Å. Grimberg)

Oat is unusual among the cereals

Fig. Oat grains at different

developmental stages

Lipid composition in

wild species of oat

(Leonova et al., Journ. of Agriculture and Food Chemistry, 2008)

Oat lines with up to 18% oil

(Peterson and Wood, Journal of Cereal Science, 1997)

6 8 10 12 14 16 18

Oil (%)

• Highest oil content among

the cereals

• Lines with up to 18% oil

by grain weight

• Increased oil was

negatively corr to starch

content

• Increased oil content was

positively corr to protein

and β-glucan content

Screening for oil quality in

cultivated oat

Oleic acid ranged from 31-40% in different cultivars

(Leonova et al., Journ. of Agriculture and Food Chemistry, 2008)

Oat oil is flavoured with with a

dash of unusual fatty acids

Increased oil content in the endosperm of cereals would be neccessary to make them

high-yielding oil crops, since the endosperm makes out the major part of the seed.

Endosperm in cereal grains

Oil localization in oat grains

Oat cultivars Freja (6% oil) and Matilda (10% oil) from Lantmännen Seed. The

difference in oil content was due to more oil in the endosperm in mature seeds.

(Banas et al., Journ Exp Bot, 2007)

(Heneen et al.,Plant Signalling and behaviour, 2009)

Light microscopy; E; Embryo, A; Aleurone, SA; SubAleurone, S; Starch, * Fused oil.

Small arrowheads; protein

Localization of oil in oat grains

Mobilization of lipid reserves in

germinating oat grains

(Leonova et al., Journ of Exp Bot, 2010)

Oat grains showing growth of the embryo and scutellum (S) after days (d) of

germination. The contour of the scutellum can be seen under the pericarp (see

arrow in b) and in the longitudinal cut of the seed (see arrows in e).

S

S S

0d 1d 2d

4d 7d 10d

c. 1st day after imbibition

g. 4th day after imbibition

(Leonova et al., Journ of Exp Bot, 2010)

Mobilization of lipid reserves in

germinating oat grains

After 4 day,scutellar epithelium (SE) cells

have elongated into the endosperm (ES)

and have come in close contact with oil

(black arrows) in the ES. Accumulation of

lipids (white arrows) are shown in the

SE.

At 1st day after imbibition, the scutellum

epithelium cells (SE) are tightly pressed

to each other and to the parenchyma

cells (SP)

All oil (TAG) was remobilized

during germination in both

cultivars

Degradation products (free

fatty acids, FFA) were taken

up by the scutellum

(Leonova et al., Journ of Exp Bot, 2010)

Mobilization of lipid reserves in

germinating oat grains

Comparative transcriptome and

metabolome study of

medium- and high-oil oat

454 sequencing of high-oil cv. Matilda endsoperm was used to develop

probes for a microarray that were hybridized with endosperm RNA from

medium-oil cv. Freja (6% oil) and Matilda (10% oil) at different

developmental stages.

(Hayden et al., The Plant Journal, 2011)

Transcript and metabolite data-

central carbon metabolism

(Hayden et al., The Plant Journal, 2011)

Comparative transcriptome and

metabolome study

• In general: Transcript levels of genes in central carbon metabolism/oil

biosynthesis were very similar but metabolite levels were very different,

between cultivars

• The high-oil cv. Matilda had much lower metabolites in glycolysis, as

well as cofactors (ATP, NADPH) needed for oil biosynthesis, comp to

medium-oil cv. Freja

• Some gene transcripts coding for starch synthesizing enzymes

(AGPase) differed between cultivars, suggesting that high oil content

might be caused by low starch synthesizing capacity

• A homolog to the transcription factor WRINKLED1 in Arabidopsis

(known to influence oil content of seeds) was found to be highly

expressed in both oat cultivars

(Hayden et al., The Plant Journal, 2011)

Carbon allocation in plant

storage tissues

Oat is very interesting to use as a model species for oil accumulation in the

cereal endosperm.

Characterization of oil

accumulation in model plant

storage tissues

7 dagar

35 dagar 42 dagar

15 dagar

StStäärkelserkelse

OljaOljaOljaOlja

StStäärkelserkelseStStäärkelserkelse

StStäärkelserkelseStStäärkelserkelseStStäärkelserkelseStStäärkelserkelse

OljaOljaOljaOlja

OljaOljaOljaOlja

OljaOlja

Jordmandel Jordmandel –– en modellven modellvääxt att omvandla xt att omvandla

sockerbeta och kassava till oljevsockerbeta och kassava till oljevääxterxter

Oat grain

endosperm

(Avena sativa)

Nutsedge tuber

parenchyma

(Cyperus

esculentus)

Aspen stem

(Populus

trichocarpa)

(Heneen et al., 2009, Turesson et al., 2010, Salla Marttila, unpublished 2013)

Nicotiana benthamiana

(tobacco) system

Agrobacterium mediated transient transformation of leaves, gives

transient gene expression. Fast system for characterizing genes.

(Method: Voinnet et al., 2003, Wood et al., 2009)

Quantification of fatty acids in TAG (triacylglycerol; oil) using

gas chromatography of fatty acid methyl esters. Highest oil in

leaves with oat WRINKLED1

Oil analyses of leaves expressing

WRINKLED1 homologs

(Grimberg et al., 2015)

Transcriptome analyses of

leaves expressing WRINKLED1

Summary

• Oats accumulate high amount of oil in

the grain

• This is due to an unusual capacity in

oats to accumulate a high proportion of

the oil in the endosperm.

• Oat oil contain a significant proportion of

polar lipids

• The oat endosperm oil is devoid (almost)

of oil bodies but our result indicate that

this oil proportion is still available as an

energy resource for the embryo during

germination

• Work towards ”high-oil” oat cultivars

focus on understanding mechanism

behind accumulation of endosperm oil.

Photo. Å. Grimberg

Theoretical oil yields of oil-oat

Rape seed (B. napus)

Seed yield: 2.5 tonnes/ha

Oil conc: 45%

Oil yield: 1.1 tonnes/ha

Oat (A. sativa)

Seed yield: 5 tonnes/ha

Oil conc: 5%

Starch conc: 60%

Oil yield: 0.25 tonnes/ha

Rape seed (B. napus)

Seed yield: 2.5 tonnes/ha

Oil conc: 45%

Oil yield: 1.1 tonnes/ha

Oat (A. sativa)

Seed yield: 3.9 tonnes/ha

Oil conc: 29%

Starch conc: 20%

Oil yield: 1.1 tonnes/ha High-oil oat

Theoretical oil yields of oil-oat

Aknowledgements

Åsa Grimberg, SLU

Svetlana Leonova, LU

Sten Stymne, SLU

Antoni Banas, Un. of Gdansk

Daniel Hayden, UC Davis

Katie Dehesh, UC Davis

Salla Marttila, SLU

Waheeb Heneen, SLU

Lantmännen Seed

• Swedish Research Council for

Environment, Agricultural

Sciences, and Spatial Planning

(Formas)

• TC4F Trees and crops for the

future (VINNOVA)

• SLU-LTJ strategic funds

• SSF Oil Crops for the Future

Photo. Å. Grimberg

Thank You