Analysis of the Arabidopsis superman allelic series and the interactions with other genes demonstrate developmental robustness and joint specification of male-female boundary, flower meristem termination and carpel compartmentalization.
SUPERMAN is a cadastral gene controlling the sexual boundary in the flower. The gene's functions and role in flower development and evolution have remained elusive. The analysis of a contrasting SUP allelic series (for which the names superman, superwoman and supersex have been coined) makes it possible to distinguish early vs. late regulatory processes at the flower meristem centre to which SUP is an important contributor. Their understanding is essential in further addressing evolutionary questions linking bisexuality and flower meristem homeostasis.



Inter-allelic comparisons were carried out and SUP interactions with other boundary factors and flower meristem patterning and homeostasis regulators (such as CLV, WUS, PAN, CUC, KNU, AG, AP3/PI, CRC and SPT) have been evaluated at genetic, molecular, morphological and histological levels.



Early SUP functions include mechanisms of male-female (sexual) boundary specification, flower mersitem termination and control of stamen number. A SUP-dependent flower meristem termination pathway is identified and analysed. Late SUP functions play a role in organ morphogenesis by controlling intra-whorl organ separation and carpel medial region formation. By integrating early and late SUP functions, and by analyzing in one single experiment a series of SUP genetic interactions, the concept of meristematic 'transference' (cascade) - a regulatory bridging process redundantly and sequentially co-ordinating the triggering and completion of flower meristem termination, and carpel margin meristem and placenta patterning - is proposed.



Taken together, the results strongly support the view that SUP(-type) function(s) have been instrumental in resolving male/female gradients into sharp male and female identities (whorls, organs) and in enforcing flower homeostasis during evolution. This has probably been achieved by incorporating the meristem patterning system of the floral axis into the female/carpel programme.
Plant Reproduction and Development, ENS de Lyon, UCBL, INRA, CNRS 69364, France.
Stéphanie
S
Breuil-Broyer
Plant Reproduction and Development, ENS de Lyon, UCBL, INRA, CNRS 69364, France.
Christophe
C
Trehin
Plant Reproduction and Development, ENS de Lyon, UCBL, INRA, CNRS 69364, France.
Patrice
P
Morel
Plant Reproduction and Development, ENS de Lyon, UCBL, INRA, CNRS 69364, France.
Véronique
V
Boltz
School of Life Sciences, Nanjing University, Nanjing City, Jiangsu Province, China 210093 Temasek Life Sciences Laboratory 1 Research Link National University of Singapore Singapore 117604.
Bo
B
Sun
Plant Reproduction and Development, ENS de Lyon, UCBL, INRA, CNRS 69364, France.
Pierre
P
Chambrier
Temasek Life Sciences Laboratory 1 Research Link National University of Singapore Singapore 117604 Nara Institute of Science and Technology 8916-5 Takayama, Ikoma, Japan.
Toshiro
T
Ito
Plant Reproduction and Development, ENS de Lyon, UCBL, INRA, CNRS 69364, France ioan.negrutiu@ens-lyon.fr.
Ioan
I
Negrutiu
D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics; D003433:Crosses, Genetic; D004268:DNA-Binding Proteins / Q000235:genetics; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D026161:MADS Domain Proteins / Q000235:genetics; D018519:Meristem / Q000235:genetics / Q000254:growth & development*; D009154:Mutation; D030821:Plants, Genetically Modified; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
C101342:APETALA 3 protein, Arabidopsis; D029681:Arabidopsis Proteins; C107294:CUC2 protein, Arabidopsis; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D026161:MADS Domain Proteins; C118078:PAN protein, Arabidopsis; D014157:Transcription Factors; C491031:knuckles protein, Arabidopsis; C096661:superman protein, Arabidopsis
Arabidopsis; SUPERMAN gene: superman, clark-kent/superwoman, supersex, AG, CLV, CRC, CUC2, KNU, PAN, SPT, WUS; allelic series; carpel; evo-devo; flower homeostasis; flower meristem determinacy; flower pattern; meristematic ‘cascade’/transference; pistillody/carpelloidy; placenta; stamen