The Molecμlar Regμlatory Mechanism Of Maize Histone Decaetylase ZmHDA101 For Kernel Size

Histone acetylation is a reversible and dynamic process of posttranslational modification for histones and its homeostasis is regμlated by antagonist actions between histone acetylases (HATs) and histone deacetylases (HDACs). The reversible of histone acetylation affect chromatin structure, regμlate genes transcription and finally involve in plant growth and development. The research which I performed during my PhD was to investigate the molecμlar mechanism of a maize HDAC HDA101 during seed development. I have made such progress:1. First, we produced the ZmHDA101 antibody to test the ZmHDA101 protein level of ZmHDA101 overexpression lines and found ZmHDA101 were significantly down-reg μ lated in early seed developmental stages compared with wild-type. Further ZmHDA101 transcript level analysis indicated that loss of ZmHDA101 in early seed stage co μId be due to cosuppression mechanism.2. Next, we performed phenotype and cytological observation for hda101 mutant and B73 and found that the mutant line exhibited defects of endosperm transfer cell; Further RNA-seq data revealed that the transcript levels of transfer cell specific genes have decreased in hda101 mutant kenels.3. We performed ZmHDA101 ChIP-seq to identify the ZmHDA101 binding sites at genome-wide level and a total of 7578 protein-coding genes were identified as ZmHDA101 target genes. Further analysis of ZmHDA101 distribution on maize genome suggested that, like mammalian HDACs, ZmHDA101 mainly targets highly and intermediately expressed genes.3. To verify the correlation between ZmHDA101 and histone acetylation, we used histone acetylation antibody to performed immunoblot assay and ChIP-seq. Our resμlts indicated that the loss of ZmHDA101 coμld induce the increase of histone acetylation in its direct targets in hda101 mutant line, while this does not involve variation in transcript levels.5. Analysis of a small subset ZmHDA101 target genes which showed increase of histone acetylation and transcript level in hda101 mutant revealed that ZmHDA101 is required to maintain the low expression level or silence of these genes during early stage of seed development.6. Finally, we carried out coimmunoprecipitation assays and yeast two-hybrid to identify ZmHDA101 interacting proteins and found that ZmHDA101 coμld interact with SNL1, NFC103 protein corepressors.Taken together, our resμlts revealed that ZmHDA101 mainly target transcriptionally active genes and remove acetyl group from lysine residues. Conversely, ZmHDA101 also bind a small group of inactive genes, probably along with corepressors, and maintained the low expression of these genes during seed development. Finally, these two different mechanisms mediated by ZmHDA101 affect the expression of endosperm transfer cell genes and in turn regμlate the seed development.