Abstract
BackgroundA key step in domestication of the grapevine was the transition from separate sexes (dioecy) in wild Vitis vinifera ssp. sylvestris (V. sylvestris) to hermaphroditism in cultivated Vitis vinifera ssp. sativa (V. vinifera). It is known that V. sylvestris has an XY system and V. vinifera a modified Y haplotype (Yh) and that the sex locus is small, but it has not previously been precisely characterized.ResultsWe generate a high-quality de novo reference genome for V. sylvestris, onto which we map whole-genome re-sequencing data of a cross to locate the sex locus. Assembly of the full X, Y, and Yh haplotypes of V. sylvestris and V. vinifera sex locus and examining their gene content and expression profiles during flower development in wild and cultivated accessions show that truncation and deletion of tapetum and pollen development genes on the X haplotype likely causes male sterility, while the upregulation of a Y allele of a cytokinin regulator (APRT3) may cause female sterility. The downregulation of this cytokinin regulator in the Yh haplotype may be sufficient to trigger reversal to hermaphroditism. Molecular dating of X and Y haplotypes is consistent with the sex locus being as old as the Vitis genus, but the mechanism by which recombination was suppressed remains undetermined.ConclusionsWe describe the genomic and evolutionary characterization of the sex locus of cultivated and wild grapevine, providing a coherent model of sex determination in the latter and for transition from dioecy to hermaphroditism during domestication.
Highlights
A key step in domestication of the grapevine was the transition from separate sexes in wild Vitis vinifera ssp. sylvestris (V. sylvestris) to hermaphroditism in cultivated Vitis vinifera ssp. sativa (V. vinifera)
We found a few candidate sex-determining genes and identified changes between the Y and Y haplotype (Yh) haplotypes that could explain the switch from dioecy to hermaphroditism during domestication
In agreement with previous work in V. vinifera, we found that the sex locus is on chromosome 2 of V. sylvestris too
Summary
A key step in domestication of the grapevine was the transition from separate sexes (dioecy) in wild Vitis vinifera ssp. sylvestris (V. sylvestris) to hermaphroditism in cultivated Vitis vinifera ssp. sativa (V. vinifera). Dioecy is rare in flowering plants (~ 6%) but over-represented among crops (~ 20%) [1] In some cases, both wild and cultivated plants are dioecious (e.g., date palm, asparagus, persimmons). Both wild and cultivated plants are dioecious (e.g., date palm, asparagus, persimmons) Other crops, such as grapevine, papaya, and strawberry, derive from dioecious progenitors and switched to hermaphroditism during domestication. A genetic analysis based on a population segregating for sex, obtained by crossing a V. vinifera genotype and an interspecific rootstock, allowed the identification of a 143-kb sex locus located on chromosome 2 in the V. vinifera reference genome [4] This particular region is not well assembled in the reference genome (PN40024—version 12X.2) [5], the F and H haplotypes being mixed both on chr and on unassembled scaffold_233 [6]. Other genetic studies in V. vinifera found different size and boundaries for the sex locus (e.g., [7, 8])
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
