Inflorescence development in tomato: linking gene … · was characterized by three metrics...
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Each output of the model, for any given dV and ΔV value, is an inflorescence, that was characterized by three metrics describing its topology: the number of flowers before the first occurence of vegetative reversion if any, the branching level, i.e., the number of phytomers initiated by the TM before being commited to make a flower and the number of vegetative axes (fig. C). These metrics were arbitrarly discretized, i.e., threshold values were fixed in order to divide the range of morphological variation created by the model in a reduced number of inflorescence types. In order to test whether the model was able to generate known mutant phenotypes, it was run for a range of ΔV (from 0 to 3) and dV (from 0 to 20) values for a total of 1200 simulations. These ranges were chosen to capture the largest variation of simulation outputs. Vegetative phase Reproductive phase SAM FM SYM FM SYM SYM F1 FM1 SYM TM IM2 IM3 IM2 IM1 IM1 Inflorescence development in tomato: linking gene function with a zigzag model Floral transition 0 3 4 5 6 7 Meristem vegetativeness [-] Floral commitment Time [plastochrons] TM IM1 IM2 SYM IM3 SAM SAM SAM F1 F2 8 FM FM dV ΔV Périlleux, C., Lobet, G., & Tocquin, P. (2014). Inflorescence architecture in tomato: gene functions within a zigzag model. Frontiers in Plant Sciences, 5(121), 1–12. LOBET G, TOCQUIN P, PERILLEUX C dV dV dV ΔV ΔV ΔV Number of flowers Branching level Number of vegetative axes terminating flower (tmf) MacAlister et al. 2012 Nature Genetics compound inflorescence (s) Quinet et al. 2006 J Exp Bot single flower truss (sft) Molinero-Rosales et al. 2004 Planta jointless (j) Szymkowiak and Irish, 1999 Plant Cell falsiflora (fa) Allen and Sussex 1996 Planta anantha (an) Allen and Sussex 1996 Planta dV ΔV MORPHOSPACE Vegetative Growth Leaf Indeterminate Meristem Flowers INTRODUCTION DISCRETISATION AND COMBINATION PARAMETERS EXPLORATION CONCEPTUALISATION ZIGZAG MODEL MORPHOSPACE MORPHOSPACE Tomato is a major crop plant and several mutants have been selected for breeding but also for isolating important genes that regulate flowering and sympodial growth. We developed a kinetic model of the tomato inflorescence development. We exploited the model to explore the diversity of morphotypes that could be generated and matched them with existing mutant phenotypes. This approach, focused on the development of the primary inflorescence, allowed us to elaborate on the genetic regulation of the kinetic model of inflorescence development. • Meristem vegetativeness decreases with time following the equation: where Vi is the current vegetativeness level of the meristem at plastochrone i, Vi−1 is its vegetativeness one plastochrone before and dV is the rate of vegetativeness decrease. dV can take different values before and after the floral transition (fig. B). • Leaf production is repressed below the floral transition threshold. • At fixed time points, meristems are allowed to produce a new phytomer, which includes an axillary meristem, unless their vegetativeness is below the floral commitment threshold. • At initiation, a lateral meristem has a higher vegetativeness level (V′0), than the meristem that produced the phytomer: where Vp is the vegetativeness (Vi) of the previous-order meristem and ΔV is the gain of vegetativeness at lateral meristem initiation. CONCLUSION We presented here a first attempt to link tomato flowering genes into a coherent network. Such network was supported by a mathematical model that was able to generate the phenotypes of a large range of single and double inflorescence mutants (fig. D). A challenging question for the future will be to integrate the spatial dynamics into the temporal models of inflorescence development, and to identify the signaling molecules that orchestrate the morphogenetic plan. @ptocquin @guillaumelobet V i = V i-1 - dV V i-1 V 0 0 = V p + ΔV Laboratoire de physiologie végétale, PhytoSYSTEMS, Université de Liège http://phytosystems.ulg.ac.be ABOUT US ABOUT THIS WORK OUR FUNDINGS After the initiation of 6–12 vegetative phytomers forming the initial segment of the plant, the SAM of tomato enters floral transition (fig. A). The last vegetative phytomer is called the sympodial (SYM) because it takes pole position and continues shoot growth after transformation of the SAM into the first inflorescence. The transitional SAM (TM), while maturing toward a flower meristem (FM) fate, initiates a new phytomer where, in contrast to vegetative phytomers, the meristematic zone (called inflorescence meristem, IM) is much prominent whereas the subtending leaflike phyllome is completely repressed. The IM will reproduce the TM programme, maturing toward the FM fate and initiating a second IM in the meantime. This reiterative process allows endless formation of flowers, providing that maturation and initiation of successive meristems keep in pace. C D B A SAM: Shoot Apical Meristem TM: Transitional Meristem SYM: Sympodial Meristem IM: Inflorescence Meristem FM: Floral Meristem F: Flower
Transcript of Inflorescence development in tomato: linking gene … · was characterized by three metrics...
Each output of the model, for any given dV and ΔV value, is an inflorescence, that was characterized by three metrics describing its topology: the number of flowers before the first occurence of vegetative reversion if any, the branching level, i.e., the number of phytomers initiated by the TM before being commited to make a flower and the number of vegetative axes (fig. C).
These metrics were arbitrarly discretized, i.e., threshold values were fixed in order to divide the range of morphological variation created by the model in a reduced number of inflorescence types. In order to test whether the model was able to generate known mutant phenotypes, it was run for a range of ΔV (from 0 to 3) and dV (from 0 to 20) values for a total of 1200 simulations. These ranges were chosen to capture the largest variation of simulation outputs.
Vegetative phase Reproductive phase
SAM
FM
SYM
FM
SYMSYM
F1 FM1
SYM
TM IM2IM3IM2
IM1IM1
I n f lo r e s c e n c e d e v e lo p m e n t i n t o m at o :l i n k i n g g e n e f u n c t i o n w i t h a z i g z a g m o d e l
Floral transition
0
3
4
5
6
7
Mer
istem
veg
etat
ivene
ss [-
]
Floral commitment
Time [plastochrons]
TM
IM1 IM2
SYM
IM3
SAM
SAM
SAM
F1 F2
8
FM FM
dV ΔV
Périlleux, C., Lobet, G., & Tocquin, P. (2014). Inflorescence architecture in tomato: gene functions within a zigzag model. Frontiers in Plant Sciences, 5(121), 1–12.
L O B E T G , T O C Q U I N P , P E R I L L E U X C
dVdV dV
ΔV
ΔV
ΔV
Number of flowers Branching level Number of vegetative axes
terminating flower (tmf)MacAlister et al. 2012
Nature Genetics
compound inflorescence (s)Quinet et al. 2006
J Exp Bot
single flower truss (sft)Molinero-Rosales et al.
2004 Planta
jointless (j)Szymkowiak and Irish,
1999 Plant Cell
falsiflora (fa)Allen and Sussex
1996 Planta
anantha (an)Allen and Sussex
1996 Planta
dV
ΔV
MORPHOSPACE
Vegetative Growth LeafIndeterminate
MeristemFlowers
INTR
ODUCT
ION
DISCRETISATION,,AND,,COMBINATION
PARAMETERS,EXPLORATION
CONCEPTUALISATION
ZIG
ZAG,M
ODEL
MORPHOSP
ACE
MORPHOSP
ACE
Tomato is a major crop plant and several mutants have been selected for breeding but also for isolating important genes that regulate flowering and sympodial growth.
We developed a kinetic model of the tomato inflorescence development. We exploited the model to explore the diversity of morphotypes that could be generated and matched them with existing mutant phenotypes. This approach, focused on the development of the primary inflorescence, allowed us to elaborate on the genetic regulation of the kinetic model of inflorescence development.
• Meristem vegetativeness decreases with time following the equation:
where Vi is the current vegetativeness level of the meristem at plastochrone i, Vi−1 is its vegetativeness one plastochrone before and dV is the rate of vegetativeness decrease. dV can take different values before and after the floral transition (fig. B).
• Leaf production is repressed below the floral transition threshold.
• At fixed time points, meristems are allowed to produce a new phytomer, which includes an axillary meristem, unless their vegetativeness is below the floral commitment threshold.
• At initiation, a lateral meristem has a higher vegetativeness level (V′0), than the meristem that produced the phytomer:
where Vp is the vegetativeness (Vi) of the previous-order meristem and ΔV is the gain of vegetativeness at lateral meristem initiation.
CONCL
USION We presented here a first attempt to link tomato flowering genes into a
coherent network. Such network was supported by a mathematical model that was able to generate the phenotypes of a large range of single and double inflorescence mutants (fig. D).
A challenging question for the future will be to integrate the spatial dynamics into the temporal models of inflorescence development, and to identify the signaling molecules that orchestrate the morphogenetic plan.
@ptocquin@guillaumelobet
Vi = Vi�1 � dVVi�1
V 00 = Vp +�V
L a b o r a t o i r e d e p h y s i o l o g i e v é g é t a l e , P h y t o S Y S T E M S , U n i v e r s i t é d e L i è g e
http://phytosystems.ulg.ac.be
ABOUT&USABOUT&THIS&WORK OUR&FUNDINGS
After the initiation of 6–12 vegetative phytomers forming the initial segment of the plant, the SAM of tomato enters floral transition (fig. A). The last vegetative phytomer is called the sympodial (SYM) because it takes pole position and continues shoot growth after transformation of the SAM into the first inflorescence. The transitional SAM (TM), while maturing toward a flower meristem (FM) fate, initiates a new phytomer where, in contrast to vegetative phytomers, the meristematic zone (called inflorescence meristem, IM) is much prominent whereas the subtending leaflike phyllome is completely repressed. The IM will reproduce the TM programme, maturing toward the FM fate and initiating a second IM in the meantime. This reiterative process allows endless formation of flowers, providing that maturation and initiation of successive meristems keep in pace.
C
D
B
A
SAM: Shoot Apical MeristemTM: Transitional MeristemSYM: Sympodial MeristemIM: Inflorescence MeristemFM: Floral MeristemF: Flower
