Summary Sex determination mechanisms in dioecious plants remain poorly understood yet offer an excellent model system to study genetic changes underlying morphological evolution. We investigated the genetic basis of sex determination in Cannabis sativa , combining quantitative trait locus mapping in a segregating population, comparative transcriptomics between monoecious and dioecious cultivars, and a genomic analysis of X–Y chromosome divergence. Quantitative trait locus mapping identified Monoecy1 , a locus on the X chromosome putatively controlling the monoecy–dioecy trait. This locus resides in the most ancient and diverged region of the sex chromosomes and contains three genes within 60,000 bp ( CsREM16 , lncREM16 and CsKAN4 ) with distinct sex‐specific and monoecy‐specific expression patterns. Monoecy1 harbors genes for male–female as well as monoecious–dioecious sex determination. We propose that the combinatorial interaction of CSREM16 , lncREM16 and CsKAN4 provides a unifying genetic framework for understanding male–female and monoecious–dioecious sex determination in C. sativa .

Summary The Polycomb repressive complex 2 (PRC2), a conserved histone methyltransferase complex, plays a central role in transcriptional silencing across eukaryotes. Here, we investigate the evolution of PWWP‐DOMAIN INTERACTORS OF POLYCOMBS (PWOs), which interact with PRC2, and examine the conservation of the PWOs‐PRC2 interaction across plant evolution by comparing orthologs from the lycophyte Selaginella moellendorffii (Sm) and the flowering plant Arabidopsis thaliana (Arabidopsis; At). Phylogenetic data traced the presence of PWO proteins across plant lineages, while protein–protein interaction assays and AlphaFold predictions assessed PWO‐PRC2 interactions and structural conservation. Functional complementation assays confirmed PWOs' conserved functions. PWO proteins are present in vascular plants but absent in bryophytes and green algae. The ancestral clade of PWO proteins includes the spikemoss Selaginella moellendorffii (Sm) PWO orthologs SmPWOa and SmPWOb. PWO proteins from vascular plants can interact with PRC2 components from multiple species, including bryophytes, which naturally lack PWOs. The PWO‐PRC2 interaction is mediated by a conserved short C‐motif. Functional and molecular assays further demonstrate that SmPWOs retain their conserved functions in Arabidopsis. Our data suggest an evolutionarily conserved role for PWOs in modulating PRC2 activity and emphasize how lineage‐specific proteins associated with conserved chromatin‐modifying complexes may shape epigenetic control mechanisms during evolution.

Summary Capsaicinoids are a class of unique alkaloids that confer the pungent taste to pepper fruits. However, it remains largely unknown how light regulates the biosynthesis of capsaicinoids. We conducted a metabolic analysis on light‐ and dark‐adapted pepper fruits. The results showed that dark‐adapted pepper fruits had lower capsaicinoid contents and correspondingly downregulated transcription of capsaicinoid biosynthetic genes (CBGs), indicating that light plays a crucial role in capsaicinoid biosynthesis. Furthermore, silencing of CaHY5 , a pivotal transcription factor gene in the light signaling pathway, decreased the content of capsaicinoid and suppressed the expression of CBGs, whereas transient overexpression of CaHY5 generated exactly opposite results. CaHY5 can bind to the G‐box motif in the promoters of CaBBX2 and CaACS8 , thereby enhancing their transcriptional levels. The activated CaBBX2 then binds to the T/G‐box in the CaACS8 promoter to stimulate its expression. CaBBX2 or CaACS8 silencing led to decreased levels of capsaicinoids, while their transient overexpression produced increased capsaicinoid contents. Collectively, our results indicated that the light‐activated CaHY5‐CaBBX2‐CaACS8 regulatory module plays a pivotal role in capsaicinoid biosynthesis. These findings provide new insights into the influence of light on capsaicinoid biosynthesis and potential targets for activation of this biosynthetic pathway in pepper.