Hark Amy T, Vlachonasios Konstantinos E, Pavangadkar Kanchan A, Rao Sumana, Gordon Hillary, Adamakis Ioannis-Dimosthenis, Kaldis Athanasios, Thomashow Michael F, Triezenberg Steven J
Biology Department, Muhlenberg College, Allentown, PA 18104, USA.
Biochim Biophys Acta. 2009 Feb;1789(2):117-24. doi: 10.1016/j.bbagrm.2008.09.003. Epub 2008 Sep 26.
Histone acetylation is an example of covalent modification of chromatin structure that has the potential to regulate gene expression. Gcn5 is a prototypical histone acetyltransferase that associates with the transcriptional coactivator Ada2. In Arabidopsis, two genes encode proteins that resemble yeast ADA2 and share approximately 45% amino acid sequence identity. We previously reported that plants harboring a T-DNA insertion in the ADA2b gene display a dwarf phenotype with developmental defects in several organs. Here we describe T-DNA insertion alleles in the ADA2a gene, which result in no dramatic growth or developmental phenotype. Both ADA2a and ADA2b are expressed in a variety of plant tissues; moreover, expression of ADA2a from a constitutive promoter fails to complement the ada2b-1 mutant phenotype, consistent with the hypothesis that the two proteins have distinct biochemical roles. To further probe the cellular roles of ADA2a and ADA2b, we studied the response of the transcriptional coactivator mutants to abiotic stress. Although ada2b seedlings display hypersensitivity to salt and abscisic acid and altered responses to low temperature stress, the responses of ada2a seedlings to abiotic stress generally parallel those of wildtype plants. Intriguingly, ada2a;ada2b double mutant plants display an intermediate, gcn5-like phenotype, suggesting that ADA2a and ADA2b each work independently with GCN5 to affect genome function in Arabidopsis.
组蛋白乙酰化是染色质结构共价修饰的一个例子，它有可能调节基因表达。Gcn5是一种典型的组蛋白乙酰转移酶，与转录共激活因子Ada2相关联。在拟南芥中，有两个基因编码类似于酵母ADA2的蛋白质，氨基酸序列同一性约为45%。我们之前报道过，在ADA2b基因中存在T-DNA插入的植物表现出矮化表型，多个器官存在发育缺陷。在这里，我们描述了ADA2a基因中的T-DNA插入等位基因，这些等位基因不会导致明显的生长或发育表型。ADA2a和ADA2b在多种植物组织中均有表达；此外，来自组成型启动子的ADA2a表达无法互补ada2b-1突变体表型，这与两种蛋白质具有不同生化作用的假设一致。为了进一步探究ADA2a和ADA2b的细胞作用，我们研究了转录共激活因子突变体对非生物胁迫的反应。虽然ada2b幼苗对盐和脱落酸表现出超敏反应，对低温胁迫的反应也有所改变，但ada2a幼苗对非生物胁迫的反应通常与野生型植物相似。有趣的是，ada2a;ada2b双突变体植物表现出一种中间的、类似gcn5的表型，这表明ADA2a和ADA2b各自独立地与GCN5协同作用，以影响拟南芥中的基因组功能。
