Functional Analysis Of Histone Demethylase JMJ705in Rice

Chromatin contains most the genetic information of eukaryotes and is the research basis of epigenetic regulation. Chromatin can be covalently modified, such as DNA methylation and histone modifications which regulate the structure of chromatin and the gene expression. Histone methylation is an important epigenetic modification in chromatin function, genome activity and gene regulation. Dimethylation or trimethylation of histone H3lysine27(H3K27me2/3) marks silent or repressed genes involved in developmental process and stress responses in plants. However, the role and the mechanism of the dynamic removal of H3K27me2/3during gene activation remain unclear. Here we study the dynamic performance of H3K27me2/3in developmental process and stress responses in plant through the research on a histone demethylase.We find a histone demethylase JMJ705which expressed in all tissues and can be induced by NaCl, abscisic acid, jasmonic acid, ethylene and rice blight bacterial by gene expression pattern analysis. JMJ705belongs to Jumonji group proteins and confirmed contain specific H3K27me3/2demethylase activity in vitro and in vivo.Overexpression of JMJ705resulted in a reduction of the overall H3K27me2/3levels in the transgenic plants. The overexpression transgenic lines displayed a leaf lesion-mimic phenotype at mature stage and the preoxidase genes, JA biosynthesis and signaling pathway genes and pathogenesis-related genes were up-regulated in overexpression lines. Then we inoculated transgenic lines with the strain of Xoo, the lesion areas in overexpression plants were less than wild plants and the bacterial growth rates were slower in overexpression plants, suggesting that elevated expression of JMJ705induces denfense-related gene expression, which may lead to enhanced plant resistance to the bacterial pathogen.We used the Affymetrix microarray platform to analyze transcriptomes of the transgenic plants. Gene ontology (GO) analysis revealed that upregulated genes were significantly enriched in the categories of stress-responsive genes. Analysis of ChIP-seq read intensity over the deregulated genes revealed that H3K27me3intensity was much higher in upregulated genes than the genome-wide average and the H3K4me3intensity displayed a lower than average level of wild-type plants. These results suggested that increased JMJ705expression preferentially activated silent or underexpressed genes that were marked by a relatively high level of H3K27me3and a relatively low level of H3K4me3.In addition, many of the upregulated genes were found to be highly induced by JA, which suggested that JA-inducible genes might be among the preferential targets of JMJ705. To study whether JMJ705plays a role in the process of JA-induced gene activation, wild-type and transgenic palnts were treated by JA, transcript levels of two JA induced genes in microarray TPS3and Os07g11739and JA-inducible marker genes PR10and JAMYB were determined by quantitative RT-PCR. The four genes showed higher expression in overexpression plants and lower expression in RNAi plants in the induction process. We measured H3K27me3levels by ChIP on JA-responsive genes in wild type, JM7705overexpression and RNAi seedings treated with JA. JA treatment reduced H3K27me3levels of four genes in wild-type plants, and the reduction of H3K27me3was more pronounced in the overexpression plants but was attenuated in the RNAi plants. These observations suggest that JMJ705was implicated in JA-induced removal of H3K27me3.