ZmEMF1a is required for the maintainence of H2Aub and H3K27me3 modifications in maize kernel development

Polycomb group (PcG) proteins can silence gene expression by modifying histones, such as H2Aub and H3K27me3, which is crucial for maintaining cell type and tissue-specific gene expression patterns. However, little is known about the impact of gene regulation by PcG proteins through H2Aub and H3K27me3 during maize kernel development.Here, we characterized a maize miniature seed mutant mn8 , and map-based cloning revealed that Mn8 encodes a plant specific PcG protein, ZmEMF1a. Mutation in ZmEMF1a leads to significantly reduced kernel size and weight. Molecular analyses showed that ZmEMF1ainteracts with PRC1 component ZmRING1 and PRC2 subunit ZmMSI1, which is required for H2Aub and H3K27me3 establishment. ZmEMF1a deficiency causes significant reduced levels of H2Aub and H3K27me3 in the genome. The combined analysis of ChIP-seq and RNA-seq data revealed that H2Aub is negatively correlated with gene expression in maize, unlike the positive association with expression of H2Aub in Arabidopsis . Compared with WT endosperms, elevated expressions of homology genes of cell proliferation repressors, such as DA1 , BB1 , ES22, MADS8 and MADS14 , accompanied with decreases in H3K27me3 or H2Aub levels at these loci in mn8 endosperms, indicating that lack of ZmEMF1a function impedes the deposition of H3K27me3 or H2Aub mark at cell division repressor genes. Taken together, our results show that ZmEMF1a plays a crucial role in regulating the expression of genes associated with maize kernel development through maintaining the modification levels of H2Aub and H3K27me3.