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.
