CHARACTERIZATION OF COCCINIA GRANDIS AS A MODEL SYSTEM TO STUDY SEX DETERMINATION IN PLANTS

Abstract

Coccinia grandis (Ivy gourd), is a dioecious member of Cucurbitaceae family, bears male and female flowers on separate individuals. The male plants carry 22A + XY and female plants carry 22A + XX chromosomes. But rare hermaphrodites with chromosome constitution as 22A + XX, bearing perfect flowers are also observed in wild. Literature survey suggests that the molecular mechanism of sex determination varies across the plant kingdom and not well understood. Till date most of the efforts to understand the mechanisms of sex determination has led to the identification of “Sex Differentiation Genes” rather than “Sex determining Genes” i.e. effect but not the cause. In this study, we have attempted to characterize the morphological differences between male, female and hermaphrodite flowers at different stages of floral development. Our observation suggests that the development of male reproductive organs is arrested in female flowers. Further, we have taken a molecular approach to understand the phylogenetic relationship as well as the genetic diversities among sexual forms of Coccinia grandis. Using universal DNA barcodes, rbcL and matK, we could establish DNA-based identification of natural hermaphrodite. Through a RAPD analysis, we have determined the genetic markers to identify the sex of the plant. We have observed that the sex expression of C. grandis is not stable. Spraying of silver nitrate (AgNO3) on female plant at an early stage of flower development produces bisexual flowers instead of female flowers. In order to understand the effect of silver nitrate on sex expression of C. grandis, we have undertaken a proteomic approach to study the male, female and AgNO3 treated flowers. Our preliminary analysis, indicate that there is differential expression of proteins in all three sexual forms of Coccinia grandis. Future investigations in this regard would unravel the function of these differentially expressed proteins in sex determination.