Molecular Mechanism Underlying Derepressed Male Production in Hexaploid Persimmon

Regulatory mechanism of MeGI on sexuality in Diospyros oleifera

Dioecy system is an important strategy for maintaining genetic diversity. The transcription factor MeGI, contributes to dioecy by promoting gynoecium development in Diospyros lotus and D. kaki. However, the function of MeGI in D. oleifera has not been identified. In this study, we confirmed that MeGI, cloned from D. oleifera, repressed the androecium development in Arabidopsis thaliana. Subsequently, chromatin immunoprecipitation-sequencing (ChIP-seq), DNA affinity purification-sequencing (DAP-seq), and RNA-seq were used to uncover the gene expression response to MeGI. The results showed that the genes upregulated and downregulated in response to MeGI were mainly enriched in the circadian rhythm-related and flavonoid biosynthetic pathways, respectively. Additionally, the WRKY DNA-binding protein 28 (WRKY28) gene, which was detected by ChIP-seq, DAP-seq, and RNA-seq, was emphasized. WRKY28 has been reported to inhibit salicylic acid (SA) biosynthesis and was upregulated in MeGI-overexpressing A. thaliana flowers, suggesting that MeGI represses the SA level by increasing the expression level of WRKY28. This was confirmed that SA level was lower in D. oleifera female floral buds than male. Overall, our findings indicate that the MeGI mediates its sex control function in D. oleifera mainly by regulating genes in the circadian rhythm, SA biosynthetic, and flavonoid biosynthetic pathways.

A convergent mechanism of sex determination in dioecious plants: Distinct sex-determining genes display converged regulation on floral B-class genes

Sex determination in dioecious plants has been broadly and progressively studied with the blooming of genome sequencing and editing techniques. This provides us with a great opportunity to explore the evolution and genetic mechanisms underlining the sex-determining system in dioecious plants. In this study, comprehensively reviewing advances in sex-chromosomes, sex-determining genes, and floral MADS-box genes in dioecious plants, we proposed a convergent model that governs plant dioecy across divergent species using a cascade regulation pathway connecting sex-determining genes and MADS-box genes e.g., B-class genes. We believe that this convergent mechanism of sex determination in dioecious plants will shed light on our understanding of gene regulation and evolution of plant dioecy. Perspectives concerning the evolutionary pathway of plant dioecy are also suggested.

The Diversity of Plant Sex Chromosomes Highlighted through Advances in Genome Sequencing

For centuries, scientists have been intrigued by the origin of dioecy in plants, characterizing sex-specific development, uncovering cytological differences between the sexes, and developing theoretical models. Through the invention and continued improvements in genomic technologies, we have truly begun to unlock the genetic basis of dioecy in many species. Here we broadly review the advances in research on dioecy and sex chromosomes. We start by first discussing the early works that built the foundation for current studies and the advances in genome sequencing that have facilitated more-recent findings. We next discuss the analyses of sex chromosomes and sex-determination genes uncovered by genome sequencing. We synthesize these results to find some patterns are emerging, such as the role of duplications, the involvement of hormones in sex-determination, and support for the two-locus model for the origin of dioecy. Though across systems, there are also many novel insights into how sex chromosomes evolve, including different sex-determining genes and routes to suppressed recombination. We propose the future of research in plant sex chromosomes should involve interdisciplinary approaches, combining cutting-edge technologies with the classics to unravel the patterns that can be found across the hundreds of independent origins.