A sequence tagged site (STS) marker encoding Copia-like retrotransposable element is associated with male specific sex expression in Momordica dioica Roxb

Momordica dioica (family—Cucurbitaceae), a perennial, dioecious climber with homomorphic sex chromosomes has been recently identified as a strategic plant for studying the early evolution of sex in angiosperms. Further, there is a greater demand for early sex identification in M. dioica because of its sex-specific medicinal and economic values. In this study, we used inter simple sequence repeat (ISSR) primers for developing a reliable molecular marker linked to sporophytic expression in M. dioica . Screening of bulked DNA pooled from male and female genotypes using 27 ISSR primers resulted in the detection of a male specific marker MdMSM . A sex-linked sequence tagged site (STS) marker MdY1 designed from MdMSM could efficiently differentiate the male and female M. dioica genotypes across different growth stages and geographical regions. Genome walking across the length of the sex-linked marker showed that MdY1 is highly homologous to the reverse transcriptase domain of a polyprotein and nested within a Copia -like retrotransposable element, MdRE1. Southern blot analysis revealed multiple copy locus and exclusive presence of MdY1 and MdRE1 only in the male genome suggesting that it might be exhibiting prominent Y-chromosome specific characteristics with strong expressions in the evolution of male sex organs. Thus, the STS marker MdY1 together with the Y-specific retroelement MdRE1 could be used as an efficient tool for early sex diagnosis in M. dioica , as well as a starting material towards characterization of traits involved in sex determination and evolutionary pathways of sexual dimorphism.