GlobaGlobal involvement of lysine crotonylation in protein modification and transcription regulation in ricel involvement of lysine crotonylation in protein modification and transcription regulation in rice

Lysine crotonylation (Kcr) is a newly discovered post-translational modification (PTM) existing in mammalian. Here, we performed a global crotonylome analysis of rice (Oryza sativa L. japonica) using high accuracy nano-LC-MS/MS in combination with crotonylated peptide enrichment. A total of 1,265 lysine crotonylation sites were identified on 690 proteins in rice seedlings. Subcellular localization analysis revealed that 51% of the crotonylated proteins identified were predicted to be associated with chloroplasts. The photosynthesis-associated proteins were also mostly enriched in total crotonylated proteins. Furthermore, to assess the relevance between histone Kcr and the genome, we performed a genomic localization analysis of histone Kcr by ChIP-seq analysis. Of the 10,923 identified peak regions, the majority (86.7%) of the enriched peaks were located in genes, especially exons. Furthermore, the degree of histone Kcr modification was positively correlated with gene expression in genic regions. Compared with other published histone modification data, the Kcr was co-located with the active histone modifications. Interestingly, histone Kcr facilitated expression of genes with existing active histone modifications. In addition, 77% of histone Kcr modifications overlapped with DNase hypersensitive sites (DHSs) in intergenic regions of the rice genome, and might mark other cis-regulatory DNA elements which are different from IPA1, a transcription activator in rice seedling. Overall, our results provide a comprehensive understanding of the biological functions of the crotonylome and new active histone modification in transcriptional regulation in plants.