HISTONE DEACETYLASE19 is involved in jasmonic acid and ethylene signaling of pathogen response in Arabidopsis

Histone acetylation is modulated through the action of histone acetyltransferases and deacetylases, which play key roles in the regulation of eukaryotic gene expression. Previously, we have identified a yeast histone deacetylase REDUCED POTASSIUM DEPENDENCY3 (RPD3) homolog, HISTONE DEACETYLASE19 (HDA19) (AtRPD3A), in Arabidopsis thaliana. Here, we report further study of the expression and function of HDA19. Analysis of Arabidopsis plants containing the HDA19:beta-glucuronidase fusion gene revealed that HDA19 was expressed throughout the life of the plant and in most plant organs examined. In addition, the expression of HDA19 was induced by wounding, the pathogen Alternaria brassicicola, and the plant hormones jasmonic acid and ethylene. Using green fluorescent protein fusion, we demonstrated that HDA19 accumulated in the nuclei of Arabidopsis cells. Overexpression of HDA19 in 35S:HDA19 plants decreased histone acetylation levels, whereas downregulation of HDA19 in HDA19-RNA interference (RNAi) plants increased histone acetylation levels. In comparison with wild-type plants, 35S:HDA19 transgenic plants had increased expression of ETHYLENE RESPONSE FACTOR1 and were more resistant to the pathogen A. brassicicola. The expression of jasmonic acid and ethylene regulated PATHOGENESIS-RELATED genes, Basic Chitinase and beta-1,3-Glucanase, was upregulated in 35S:HDA19 plants but downregulated in HDA19-RNAi plants. Our studies provide evidence that HDA19 may regulate gene expression involved in jasmonic acid and ethylene signaling of pathogen response in Arabidopsis.     

CHB2, a member of the SWI3 gene family,is a global regulator in Arabidopsis

The SWI/SNF complex is an ATP-dependent chromatin remodeling complex that plays an important role in the regulation of eukaryotic gene expression. Very little is known about the function of SWI/SNF complex in plants compared with animals and yeast. SWI3 is one of the core components of the SWI/SNF chromatin remodeling complexes in yeast. We have identified a putative SWI3-like cDNA clone, CHB2 (AtSWI3B), from Arabidopsis thaliana by screening the expressed sequence tag database. CHB2 encodes a putative protein of 469 amino acids and shares 23% amino acid sequence identity and 64% similarity with the yeast SWI3. The Arabidopsis genome contains four SWI3-like genes, namely CHB1 (AtSWI3A), CHB2 (AtSWI3B), CHB3 (AtSWI3C) and CHB4 (AtSWI3D). The expression of CHB2, CHB3 and CHB4 mRNA was detected in all tissues analyzed by RT-PCR. The expression of CHB1 mRNA, however, could not be detected in the siliques, suggesting that there is differential expression among CHB genes in different Arabidopsis tissues. To investigate the role of CHB2 in plants, Arabidopsis plants were transformed with a gene construct comprising a CHB2 cDNA in the antisense orientation driven by the CaMV 35S promoter. Repression of CHB2 expression resulted in pleiotropic developmental abnormalities including abnormal seedling and leaf phenotypes, dwarfism, delayed flowering and no apical dominance, suggesting a global role for CHB2 in the regulation of gene expression. Our results indicate that CHB2 plays an essential role in plant growth and development.     

浅谈干扰素（及其诱导物poly 1:C)抗病毒作用的分子基基础

《遗传》杂志是全国性中级学术刊物。其专业领域涉及遗传学各个分支学科。凡有关人类与医学A传、植物遗 传、动物遗传、微生物遗传方面的研究报告、快讯、实验技术与方法、综述、讲座、争鸣、讨论、教学心得等文章,均受 本刊欢迎。质量优秀者优先发表。来稿暂不收审稿费,发表后暂不收版面费,而且照付稿酬,质量优秀的文章稿 酬从优。目前尤其欢迎微生物遗传学方面的稿件,发表优先。     

HD2C interacts with HDA6 and is involved in ABA and salt stress response in Arabidopsis

HD2 proteins are plant specific histone deacetylases. Four HD2 proteins, HD2A, HD2B, HD2C, and HD2D, have been identified in Arabidopsis. It was found that the expression of HD2A, HD2B, HD2C, and HD2D was repressed by ABA and NaCl. To investigate the function of HD2 proteins further, two HD2C T-DNA insertion lines of Arabidopsis, hd2c-1 and hd2c-3 were identified. Compared with wild-type plants, hd2c-1 and hd2c-3 plants displayed increased sensitivity to ABA and NaCl during germination and decreased tolerance to salt stress. These observations support a role of HD2C in the ABA and salt-stress response in Arabidopsis. Moreover, it was demonstrated that HD2C interacted physically with a RPD3-type histone deacetylase, HDA6, and bound to histone H3. The expression of ABA-responsive genes, ABI1 and ABI2, was increased in hda6, hd2c, and hda6/hd2c-1 double mutant plants, which was associated with increased histone H3K9K14 acetylation and decreased histone H3K9 dimethylation. Taken together, our results suggested that HD2C functionally associates with HDA6 and regulates gene expression through histone modifications.     

组蛋白脱乙酰化酶及其与基因转录的关系

含有组蛋白脱乙酰化酶活性的分子有两类：一类是与酵母RPD3同源的分子,另一类是与RPD3不同源的分子.它们各有其不同的来源,存在于各自的复合物中,催化不完全相同的组蛋白或其他蛋白质脱乙酰化;这些脱乙酰化酶与基因转录的调控存在着密切的关系, 主要是介导基因转录的抑制.     

Histone acetylation regulates the time of replication origin firing

The temporal firing of replication origins throughout S phase in yeast depends on unknown determinants within the adjacent chromosomal environment. We demonstrate here that the state of histone acetylation of surrounding chromatin is an important regulator of temporal firing. Deletion of RPD3 histone deacetylase causes earlier origin firing and concurrent binding of the replication factor Cdc45p to origins. In addition, increased acetylation of histones in the vicinity of the late origin ARS1412 by recruitment of the histone acetyltransferase Gcn5p causes ARS1412 alone to fire earlier. These data indicate that histone acetylation is a direct determinant of the timing of origin firing.     

Lysine acetylome profiling uncovers novel histone deacetylase substrate proteins in Arabidopsis

Histone deacetylases have central functions in regulating stress defenses and development in plants. However, the knowledge about the deacetylase functions is largely limited to histones, although these enzymes were found in diverse subcellular compartments. In this study, we determined the proteome‐wide signatures of the RPD3/HDA1 class of histone deacetylases in Arabidopsis. Relative quantification of the changes in the lysine acetylation levels was determined on a proteome‐wide scale after treatment of Arabidopsis leaves with deacetylase inhibitors apicidin and trichostatin A. We identified 91 new acetylated candidate proteins other than histones, which are potential substrates of the RPD3/HDA1‐like histone deacetylases in Arabidopsis, of which at least 30 of these proteins function in nucleic acid binding. Furthermore, our analysis revealed that histone deacetylase 14 (HDA14) is the first organellar‐localized RPD3/HDA1 class protein found to reside in the chloroplasts and that the majority of its protein targets have functions in photosynthesis. Finally, the analysis of HDA14 loss‐of‐function mutants revealed that the activation state of RuBisCO is controlled by lysine acetylation of RuBisCO activase under low‐light conditions.