Regulatory Mechanism Of Rice Histone Deacetylase OsSRT1 In Seed Starch Development And Glycolysis

Rice(Oryza sativa)is one of most important food crops in the world,so it is important to study the metabolism regulation in rice.Histone modification play important roles in rice development and stress resistance,including methylation,acetylation,phosphorylation,ubiquitination and others.There are few reports on the epigenetic regulation of rice metaboliam.Os SRT1,a member of SILENT INFORMATION REGULATOR2(SIR2)family proteins,regulatre histone H3K9(lysine-9 of H3)acetylation in rice.Os SRT1 RNA interference induced an increase of histone H3K9 acetylation,leading to lesions mimicking plant hypersensitive responses,whereas overexpression of Os SRT1 enhanced tolerance to oxidative stress.Based on the research of Dr.Huang(Huang et al 2007),we focused on the regulation of starch metabolism and glycolysis.Main results are shown as following:1.The seed setting rate in Os SRT1 RNAi plants was much less than in WT plants and Os SRT1 RNAi seeds was retarded at the 3 DAP(days after pollination).2.Semi-thin sections and Lugol’s staining revealed no starch accumulation in Os SRT1 RNAi endosperm cells and pericarp cells at 3 DAP.3.RSR1 and amylase genes are up-regulated in Os SRT1 RNAi seed at 2 DAP.4.Os SRT1 regulates H3K9 ac on RSR1 and amylase genes at the early stage of seed development.5.OsSRT1 directly binds to the amylase genes to regulates H3K9 ac in seeds at 2 DAP.6.SRT1 represses transposable element-related genes by H3K9 deacetylation in seeds at 2DAP.7.KEGG analysis of the H3K9 ac up-regulated genes in Os SRT1 RNAi seedlings revealed that Os SRT1 represses glycolysis.8.Assays of Pull-down,Bi FC and Co-IP verificate the interaction between Os SRT1 and GAPDH proteins in rice.9.Transcripts of other glycolytic genes were reduced in a T-DNA mutant line of Os GAPDH1,thus Os GAPDH1 was required for expression of glycolytic genes.10.Os GAPDH1 trans-activates glycolytic gene promoters and Os SRT1 was necessary to inhibit Os GAPDH1-mediated gene activation.11.Rice GAPDH1 were acetylated and Os SRT1 could deacetylate Os GAPDH1.12.The nuclear accumulation of Os GAPDH is enhanced by oxidative stresses and Os SRT1 regulates nuclear accumulation of Os GAPDH1.Those data demonstrated that Os SRT1 was required to reduce histone H3K9 acetylation on starch metabolism genes and transposons in developing seeds,involving in starch accumulation and transposon repression to ensure normal seed development.Moreover,Os SRT1 interacts with the rice glycolytic GAPDH that functions as an activator of glycolytic genes.The lysine acetylation,nuclear accumulation,and transcriptional activity of GAPDH are negatively regulated by Os SRT1.The results indicate that in addition to epigenetic regulation of gene expression,Os SRT1 regulates carbon metabolic flux by mediating deacetylation and repression of GAPDH transcriptional function of glycolysis activation in rice.