Chloroplast transcription at different light intensities.: Glutathione-mediated phosphorylation of the major RNA polymerase involved in redox-regulated organellar gene expression
Chloroplast transcription at different light intensities.: Glutathione-mediated phosphorylation of the major RNA polymerase involved in redox-regulated organellar gene expression
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DOI：
10.1104/pp.010168
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发表时间：
2001-11-01
期刊：
影响因子：
7.4
通讯作者：
Link, G
中科院分区：
文献类型：
--
作者：
Baena-González, E;Baginsky, S;Link, G
以前，使用芥菜（白芥）叶绿体纯化的RNA聚合酶的研究表明，相关的蛋白激酶的转录控制。发现这种激酶对谷胱甘肽（GSH）介导的可逆巯基/二硫键形成有反应，尽管浓度超过了认为存在于体内的浓度。在本研究中，提出了几条证据来证实这种调节机制的功能，也在体内：（a）对聚合酶相关的转录激酶的研究表明，在适当的ATP水平下，与体内类似的GSH浓度足以调节激酶活性;（B）从分离的芥菜叶绿体中测量的GSH对光强度的反应显示出相当大的差异;（c）这反映在分离的叶绿体中的连续转录率上，与生长光条件相比，如果细胞器是从强光下培养的幼苗制备的，则通常更高;（d）体外实验证实，激酶不仅影响光合作用基因（psbA）的转录，还影响非光合作用基因（return（）;和（e）聚合酶-激酶复合物揭示了多肽磷酸化状态的特异性差异，这取决于叶绿体分离之前幼苗所暴露的光强度。两者合计，这些数据是一致的GSH和磷酸化依赖的调节叶绿体在体内的转录。
Previous, studies using purified RNA polymerase from mustard (Sinapis alba) chloroplasts showed control of transcription by an associated protein kinase. This kinase was found to respond to reversible thiol/disulfide formation mediated by glutathione (GSH), although at concentrations exceeding those thought to exist in vivo. In the present study, several lines of evidence are presented to substantiate the functioning of this regulation mechanism, also in vivo: (a) Studies on the polymerase-associated transcription kinase revealed that at appropriate ATP levels, GSH concentrations similar to those in vivo are sufficient to modulate the kinase activity; (b) GSH measurements from isolated mustard chloroplasts showed considerable differences in response to light intensity; (c) this was reflected by run-on transcription rates in isolated chloroplasts that were generally higher if organelles were prepared from seedlings incubated under high-light as compared with growth-light conditions; (d) the notion of a general transcriptional switch was strengthened by in vitro experiments showing that the kinase not only affects the transcription of a photosynthetic gene (psbA) but also that of a nonphotosynthetic gene (trnQ); and (e) the polymerase-kinase complex revealed specific differences in the phosphorylation state of polypeptides depending on the light intensity to which the seedlings had been exposed prior to chloroplast isolation. Taken together, these data are consistent with GSH and phosphorylation-dependent regulation of chloroplast transcription in vivo.