Genome-Wide Analysis of the Rice PcG Gene Family and Its Involvement in Salt Response and Development

Polycomb group (PcG) proteins are pivotal in maintaining gene silencing through epigenetic mechanisms, particularly by catalyzing Histone H3 lysine 27 trimethylation (H3K27me3) via the Polycomb Repressive Complex 2 (PRC2) complex. These modifications are crucial for regulating developmental pathways and environmental stress responses in plants. Despite their importance, the PcG gene family has not been systematically explored in rice (Oryza sativa). In this study, 15 OsPcG genes were identified in the Nipponbare genome, spanning 12 chromosomes and classified into distinct phylogenetic groups. Structural and conserved motif analyses revealed high sequence conservation, while collinearity and Ka/Ks analyses indicated gene family expansion through segmental duplication under purifying selection. Promoter element prediction suggested that many OsPcG genes are responsive to plant hormones and abiotic stress cues. Transcriptome analysis under salt treatment highlighted OsPcG5 as a key salt-responsive gene, with qRT-PCR confirming its dynamic expression. Subcellular localization showed OsPcG5 residing in both the nucleus and plasma membrane, suggesting multifunctional roles. Additionally, overexpression of OsFIE2—a PRC2 component—resulted in elevated H3K27me3 levels and abnormal plant height, linking it to chromatin modification and development. These findings contribute to our understanding of PcG gene functions in rice and offer potential genetic resources for enhancing salt tolerance through epigenetic approaches.