The dynamic regulatory network of stamens and pistils in papaya

Papaya exhibits three sex types: female (XX), male (XY), and hermaphrodite (XY^h), making it an unusual trioecious model for studying sex determination. A critical aspect of papaya sex determination is the pistil abortion in male flowers. However, the regulatory networks that control the development of pistils and stamens in papaya remain incompletely understood.

In this study, we identified three organ-specific clusters involved in papaya pistils and stamens development. We found that pistil development is primarily characterized by the significant expression of auxin-related genes, while the pistil abortion genes in males is mainly associated with cytokinin, gibberellin, and auxin pathways. Additionally, we constructed expression regulatory networks for the development of female pistils, aborted pistils and stamens in male flowers, revealing key regulatory genes and signaling pathways involved in papaya organ development. Furthermore, we systematically identified 65 members of the MADS-box gene family and 10 ABCDE subfamily MADS-box genes in papaya. By constructing a phylogenetic tree of the ABCDE subfamily, we uncovered gene contraction and expansion in papaya, providing an improved understanding of the developmental mechanisms and evolutionary history of papaya floral organs.

These findings provide a robust framework for identifying candidate sex-determining genes and constructing the sex determination regulatory network in papaya, providing insights and genomic resources for papaya breeding.