The sex determinism of the melon is governed by two genes, andromonoecy (a) and gynoecy (g), and variations in the interactions between them result in a broad distribution of sexual types. Plants can be monoecious with an A/-, G/- genotype (bearing male and female flowers). Plants with the a/a, G/- genotype are andromonoecious (bearing male and hermaphrodite flowers). Plants with the A/-, g/g genotype are gynoecious (bearing female flowers only) and those with the a/a, g/g genotype are hermaphrodite. In addition, sex determinism in the melon is also influenced by the processing of plant hormones such as ethylene.
INRA researchers in Evry and Avignon have isolated the genomic region responsible for andromonoecy and demonstrated that this gene codes for an enzyme implicated in ethylene synthesis. Having studied natural variations of the gene in 500 melon varieties from all parts of the world, they have shown that andromonoecy is linked to the replacement of one base by another in the gene, leading to a mutation that inactivates the enzyme that is functional during the development of female flowers.
The scientists have shown that the production of ethylene linked to this enzyme prevents the development of stamens (male organs) in female flowers. Mutation of the gene coding for this enzyme allows the formation of male organs and hence hermaphrodite flowers. Such a link between sex determinism and hormonal synthesis has also been revealed in other plants, such as maize.
Andromonoecy appears to be more common in cultivated than in wild plants. According to this study, the mutation probably appeared recently and was then positively selected because it was either associated with a better allocation of resources by the plant towards reproductive organs, or with a positive relationship between the number of male flowers and species survival. It is now necessary to better assess the selective advantage procured by andromonoecy in both the melon and in other plants.
This work has been the subject of a patent, filed under the reference FR 0651538 and published as number WO2007125264 "Système génétique pour le contrôle du développement du type floral d’une plante dicotylédone, et mise en œuvre dans des procédés de détection et de sélection".
Reference:
‘A Conserved Mutation in an Ethylene Biosynthesis Enzyme Leads to Andromonoecy in Melons’
Science Vol 321, n° 5890 – 8 August 2008
Adnane Boualem,1 Mohamed Fergany,1 Ronan Fernandez,1 Christelle Troadec,1Antoine Martin,1 Halima Morin,2 Marie-Agnes Sari,3 Fabrice Collin,3 Jonathan M. Flowers,4Michel Pitrat,5 Michael D. Purugganan,4 Catherine Dogimont,5 Abdelhafid Bendahmane1
1 INRA–CNRS, UMR1165, Unité de Recherche en Génomique Végétale, 2 rueGaston Crémieux, F-91057 Evry.
2 INRA, Laboratoire de Biologie Cellulaire, Institut Jean Pierre Bourgin, F-78026
Versailles.
3 CNRS, UMR 8601, Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, Université René Descartes, 45 Rue des Saint-Pères, F-75270 Paris.
4 Department of Biology, Center for Genomics and Systems Biology, 100 Washington Square East, New York University, New York, NY 10003, U.S.A.
5 INRA, Unité de Génétique et d'Amélioration des Fruits et Légumes, BP 94, F-84143 Montfavet.
|
Search:
