# Subfunctionalization of CpSVP-Y Paralog Contributes to Male Reproductive Fitness in Papaya

## TL;DR

A gene on the Y chromosome in papayas helps male plants grow longer flower stalks, improving their reproductive success.

## Contribution

The study identifies subfunctionalization of the CpSVP-Y gene as a mechanism contributing to male reproductive fitness in papayas.

## Key findings

- The male allele CpSVP-Y rescues both pedicel elongation and flowering time in Arabidopsis.
- The autosomal allele CpSVP-A only affects pedicel elongation and not flowering time.
- CpSVP-Y is retained for both functions, while CpSVP-A likely lost the flowering time function.

## Abstract

Papayas possess three sex genotypes: female XX, male XY, and hermaphrodite XYh. Only male plants produce long peduncles with numerous flowers, a trait that improves reproductive success. The gene SHORT VEGETATIVE PHASE (CpSVP) is located on the Y chromosome, absent from the X chromosome, and disrupted in the Yh chromosome, making it a key candidate gene for long peduncles in male plants. An autosomal CpSVP allele (CpSVP-A) was also annotated in a papaya genome. The overexpression of the male allele in Arabidopsis increases pedicel length, which supports its role in pedicel elongation. Unexpectedly, the autosomal allele CpSVP-A produced a similar phenotype as the male one, while the hermaphroditic allele (CpSVP-Yh) did not cause any significant change in pedicel length. Additionally, only the male allele rescued early flowering in an Atsvp mutant, indicating that it regulates both pedicel length and flowering time. In contrast, the autosomal allele only affected pedicel elongation and had no effect on flowering time. Together, these results demonstrate that CpSVP-Y underwent subfunctionalization, retaining both peduncle elongation and flowering time functions, while CpSVP-A likely lost the latter. Thus, CpSVP-Y contributes to male reproductive fitness through enhanced peduncle development without affecting sex determination, potentially regulated by Y chromosome-specific cis-elements. This study provides new insights into the genetic basis of sexually dimorphic traits in papayas.