Investigating sex expression and modification in dioecious coccinia grandis through an integrated transcriptomic and proteomic approach

Abstract

Majority of the angiosperm species are co sexual Only 6 of angiosperm species are dioecious having separate male and female individuals Coccinia grandis is one such dioecious species having heteromorphic sex chromosomes Male 22A XY and Female 22A XX C grandis belongs to Cucurbitaceae a family known for its diverse sexual systems We have also identified a rare gynomonoecious form of C grandis 22 XX that bears pistillate GyM F and hermaphrodite flowers GyM H Interestingly application of silver nitrate AgNO3 on female plants induces stamen development leading to the formation of morphologically hermaphrodite flowers Ag H A comprehensive morphological histological and cytological characterization of flower buds has been carried out Pollen viability assays and mating experiments showed that pollens from GyM H and Ag H flowers were sterile We have also assembled a de novo transcriptome from RNA Seq of flower buds of all sexes at early and middle stages of development followed by differential gene expression analyses to identify sex biased genes Simultaneously our proteomic approach has resulted in detection of 3385 proteins and many of these were expressed in a sex biased manner Ethylene responses were suppressed in both male and Ag H compared to female buds suggesting a probable role of ethylene in stamen suppression similar to monoecious cucurbits such as melon and cucumber Also pollen fertility associated GO terms were depleted in middle staged GyM H buds compared to male buds indicating the necessity of Y chromosome for pollen fertility In absence of a genetic transformation tool we have standardized an efficient ALSV mediated virus induced gene silencing VIGS technique in C grandis Overall this study has enabled the identification of new sex biased genes for further investigation of stamen arrest pollen fertility and AgNO3 mediated sex modification in C grandis Additionally the VIGS technique standardized in this study would be useful for the functional characterization of such sex biased genes newline newline