Diversification and evolution of the Polycomb group family in nine Rosaceae species and molecular characteristics of PmLHP1

• 1310 Polycomb group proteins were identified in 17 plant species. • 383 Polycomb Repressive Complex 1 were identified in nine Rosaceae species. • The members of the LHP1 section had the highest probability of phase separation. • PmLHP1 exhibits high sequence similarity with orthologs in other woody plants. • The localization of PmLHP1 in the nucleus changes with high temperatures. Polycomb group (PcG) proteins play a crucial role in the regulatory network of plant growth, development, and environmental stress responses, serving as important epigenetic regulators. However, a systematic comparative investigation of PcG proteins across the Rosaceae family is still lacking. In this study, we identified 721 PcG genes in nine Rosaceae species, including 383 members of Polycomb Repressive Complex 1 (PRC1). Phylogenetic analysis, conserved motifs and domain characterization, chromosomal localization, collinearity analysis, and cis-regulatory element prediction indicate that PRC1 proteins participate in plant development and various biological processes. Through extensive phylogenetic analyses, these PcG proteins were classified into nine subfamilies: RING1, BMI1, LHP1, EMF1, VRN1, E(z), Esc, N55, and Su(z)12. These analyses further demonstrated that plant PcG proteins originate from a common ancestor and have shown that PRC1 components are diverged in bryophytes. LHP1 has been shown to be involved in the development of flower epigenetic silencing of genes. Bioinformatics analysis revealed that PmLHP1 exhibits high sequence similarity with orthologs in other woody plants, and its two major structural domains are highly conserved. Given the established role of phase separation in temperature-dependent regulation of plant growth and development, we assessed the likelihood of phase separation among PRC1 components in Rosaceae. Notably, members of the LHP1 subfamily showed high propensity for phase separation. After isolating PmLHP1 from Prunus mume , subcellular localization analysis confirmed its nuclear localization. Furthermore, PmLHP1 exhibited temperature-dependent localization changes under high-temperature conditions. Overall, this study provides new perspectives on the evolutionary dynamics of the PcG family in Rosaceae and the functional role of PmLHP1 in P. mume development.