A small XY chromosomal region explains sex determination in wild dioecious V. vinifera and the reversal to hermaphroditism in domesticated grapevines
1 Centre de Bio-Archéologie et d¿Ecologie CBAE (UMR 5059 CNRS/Université Montpellier 2/EPHE/INRAP). Equipe Interactions, Biodiversité, Sociétés, Institut de Botanique, 163 rue Auguste Broussonet, Montpellier, 34090, France
2 INRA, UMR 1334 AGAP, Equipe Diversité, Adaptation et Amélioration de la Vigne, Montpellier, F34060, France
3 Institute of Horticulture, Viticulture and Oenology, Agrarian University of Georgia, University Campus at Digomi, David Aghmashenebeli Alley, 13-th km. 0159, Tbilisi, Georgia
4 CBGP-INIA. Dpto Biotecnología, Campus de Montegancedo, Autovía M40, km38, Pozuelo de Alarcón, 28223, Madrid, Spain
5 Université Montpellier 2, Place Eugène Bataillon, Montpellier, 34095, France
BMC Plant Biology 2014, 14:229 doi:10.1186/s12870-014-0229-zPublished: 3 September 2014
In Vitis vinifera L., domestication induced a dramatic change in flower morphology: the wild sylvestris subspecies is dioecious while hermaphroditism is largely predominant in the domesticated subsp. V. v. vinifera. The characterisation of polymorphisms in genes underlying the sex-determining chromosomal region may help clarify the history of domestication in grapevine and the evolution of sex chromosomes in plants. In the genus Vitis, sex determination is putatively controlled by one major locus with three alleles, male M, hermaphrodite H and female F, with an allelic dominance M?>?H?>?F. Previous genetic studies located the sex locus on chromosome 2. We used DNA polymorphisms of geographically diverse V. vinifera genotypes to confirm the position of this locus, to characterise the genetic diversity and traces of selection in candidate genes, and to explore the origin of hermaphroditism.
In V. v. sylvestris, a sex-determining region of 154.8 kb, also present in other Vitis species, spans less than 1% of chromosome 2. It displays haplotype diversity, linkage disequilibrium and differentiation that typically correspond to a small XY sex-determining region with XY males and XX females. In male alleles, traces of purifying selection were found for a trehalose phosphatase, an exostosin and a WRKY transcription factor, with strikingly low polymorphism levels between distant geographic regions. Both diversity and network analysis revealed that H alleles are more closely related to M than to F alleles.
Hermaphrodite alleles appear to derive from male alleles of wild grapevines, with successive recombination events allowing import of diversity from the X into the Y chromosomal region and slowing down the expansion of the region into a full heteromorphic chromosome. Our data are consistent with multiple domestication events and show traces of introgression from other Asian Vitis species into the cultivated grapevine gene pool.