A Nucleus-Encoded Chloroplast Phosphoprotein Governs Expression of the Photosystem I Subunit PsaC in Chlamydomonas reinhardtii
A Nucleus-Encoded Chloroplast Phosphoprotein Governs Expression of the Photosystem I Subunit PsaC in Chlamydomonas reinhardtii
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DOI：
10.1105/tpc.15.00725
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发表时间：
2016-05-01
期刊：
影响因子：
11.6
通讯作者：
Goldschmidt-Clermont, Michel
中科院分区：
文献类型：
--
作者：
Douchi, Damien;Qu, Yujiao;Goldschmidt-Clermont, Michel
核质区室通过大量干预转录后步骤的蛋白质对叶绿体基因表达进行顺行控制。在这里，我们发现莱茵衣藻 psaC 突变体 (mac1) 的成熟在光系统 I 中存在缺陷，并且无法积累 psaC mRNA。 MAC1 基因座编码超螺旋重复蛋白半 A-四肽 (HAT) 家族的成员，其中一些参与 RNA 交易。 Mac1 蛋白定位于可溶部分中的叶绿体。 MAC1 通过 psaC 转录本的 59 个非翻译区发挥作用，并且是其稳定性所必需的。野生型中映射到 psaC RNA 5' 端但 mac1 突变体中不映射的小 RNA 被推断代表 MAC1 依赖性蛋白结合的足迹，并且细菌中表达的 Mac1 在体外结合 RNA。对缺铁的协调反应会导致光合电子传递链，特别是光系统 I 的解体，也会导致 Mac1 的减少。 Mac1 的过度表达会导致 psaC mRNA 的平行增加，但不会导致 PsaC 蛋白的增加，这表明 Mac1 可能限制 psaC mRNA 的积累，但其他过程调节蛋白质的积累。此外，Mac 1 会根据铁的可用性和改变电子传递链氧化还原平衡的条件而发生差异性磷酸化。
The nucleo-cytoplasmic compartment exerts anterograde control on chloroplast gene expression through numerous proteins that intervene at posttranscriptional steps. Here, we show that the maturation of psaC mutant (mac1) of Chlamydomonas reinhardtii is defective in photosystem I and fails to accumulate psaC mRNA. The MAC1 locus encodes a member of the Half-A-Tetratricopeptide (HAT) family of super-helical repeat proteins, some of which are involved in RNA transactions. The Mac1 protein localizes to the chloroplast in the soluble fraction. MAC1 acts through the 59 untranslated region of psaC transcripts and is required for their stability. Small RNAs that map to the 5'end of psaC RNA in the wild type but not in the mac1 mutant are inferred to represent footprints of MAC1-dependent protein binding, and Mac1 expressed in bacteria binds RNA in vitro. A coordinate response to iron deficiency, which leads to dismantling of the photosynthetic electron transfer chain and in particular of photosystem I, also causes a decrease of Mac1. Overexpression of Mac1 leads to a parallel increase in psaC mRNA but not in PsaC protein, suggesting that Mac1 may be limiting for psaC mRNA accumulation but that other processes regulate protein accumulation. Furthermore, Mac 1 is differentially phosphorylated in response to iron availability and to conditions that alter the redox balance of the electron transfer chain.