College of Life Sciences, Nanjing Normal University, Jiangsu 210046, China.
Plant Physiol. 2011 Dec;157(4):1733-45. doi: 10.1104/pp.111.184762. Epub 2011 Oct 18.
The SET domain-containing protein, pTAC14, was previously identified as a component of the transcriptionally active chromosome (TAC) complexes. Here, we investigated the function of pTAC14 in the regulation of plastid-encoded bacterial-type RNA polymerase (PEP) activity and chloroplast development. The knockout of pTAC14 led to the blockage of thylakoid formation in Arabidopsis (Arabidopsis thaliana), and ptac14 was seedling lethal. Sequence and transcriptional analysis showed that pTAC14 encodes a specific protein in plants that is located in the chloroplast associated with the thylakoid and that its expression depends on light. In addition, the transcript levels of all investigated PEP-dependent genes were clearly reduced in the ptac14-1 mutants, while the accumulation of nucleus-encoded phage-type RNA polymerase-dependent transcripts was increased, indicating an important role of pTAC14 in maintaining PEP activity. pTAC14 was found to interact with pTAC12/HEMERA, another component of TACs that is involved in phytochrome signaling. The data suggest that pTAC14 is essential for proper chloroplast development, most likely by affecting PEP activity and regulating PEP-dependent plastid gene transcription in Arabidopsis together with pTAC12.
SET 结构域蛋白 pTAC14 先前被鉴定为转录活性染色体 (TAC) 复合物的组成部分。在这里，我们研究了 pTAC14 在调节质体编码的细菌型 RNA 聚合酶 (PEP) 活性和叶绿体发育中的功能。pTAC14 的敲除导致拟南芥 (Arabidopsis thaliana) 中类囊体的形成受阻，ptac14 是幼苗致死的。序列和转录分析表明，pTAC14 编码一种在植物中特异性的蛋白，位于与类囊体相关的叶绿体中，其表达依赖于光。此外，在 ptac14-1 突变体中，所有研究的 PEP 依赖性基因的转录水平明显降低，而核编码噬菌体型 RNA 聚合酶依赖性转录物的积累增加，表明 pTAC14 在维持 PEP 活性方面起着重要作用。发现 pTAC14 与 TAC 的另一个组成部分 pTAC12/HEMERA 相互作用，该蛋白参与光信号转导。数据表明，pTAC14 对于正常的叶绿体发育是必不可少的，很可能通过影响 PEP 活性并与 pTAC12 一起调节 Arabidopsis 中 PEP 依赖性质体基因转录来实现这一功能。
