Wostrikoff K, Choquet Y, Wollman F A, Girard-Bascou J
UPR/CNRS 1261, Institut de Biologie Physico-Chimique, 75005 Paris, France.
Genetics. 2001 Sep;159(1):119-32. doi: 10.1093/genetics/159.1.119.
We isolated seven allelic nuclear mutants of Chlamydomonas reinhardtii specifically blocked in the translation of cytochrome f, a major chloroplast-encoded subunit of the photosynthetic electron transport chain encoded by the petA gene. We recovered one chloroplast suppressor in which the coding region of petA was now expressed under the control of a duplicated 5' untranslated region from another open reading frame of presently unknown function. Since we also recovered 14 nuclear intragenic suppressors, we ended up with 21 alleles of a single nuclear gene we called TCA1 for translation of cytochrome b(6)f complex petA mRNA. The high number of TCA1 alleles, together with the absence of genetic evidence for other nuclear loci controlling translation of the chloroplast petA gene, strongly suggests that TCA1 is the only trans-acting factor. We studied the assembly-dependent regulation of cytochrome f translation--known as the CES process--in TCA1-mutated contexts. In the presence of a leaky tca1 allele, we observed that the regulation of cytochrome f translation was now exerted within the limits of the restricted translational activation conferred by the altered version of TCA1 as predicted if TCA1 was the ternary effector involved in the CES process.
我们分离出莱茵衣藻的七个等位核突变体，它们在细胞色素f的翻译过程中被特异性阻断，细胞色素f是由petA基因编码的光合电子传递链中一个主要的叶绿体编码亚基。我们获得了一个叶绿体抑制子，其中petA的编码区现在受来自另一个功能未知的开放阅读框的重复5'非翻译区的控制而表达。由于我们还获得了14个核内基因抑制子，最终得到了一个单一核基因的21个等位基因，我们将其命名为TCA1，用于细胞色素b(6)f复合物petA mRNA的翻译。TCA1等位基因数量众多，且缺乏其他控制叶绿体petA基因翻译的核基因座的遗传证据，这强烈表明TCA1是唯一的反式作用因子。我们研究了在TCA1突变背景下细胞色素f翻译的组装依赖性调控——即所谓的CES过程。在存在渗漏性tca1等位基因的情况下，我们观察到细胞色素f翻译的调控现在是在TCA1改变版本赋予的有限翻译激活范围内发挥作用的，正如如果TCA1是参与CES过程的三元效应器所预测的那样。
