Chloroplast quality control pathways are dependent on plastid DNA synthesis and nucleotides provided by cytidine triphosphate synthase two
Chloroplast quality control pathways are dependent on plastid DNA synthesis and nucleotides provided by cytidine triphosphate synthase two
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DOI：
10.1111/nph.17467
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发表时间：
2021-06-21
期刊：
影响因子：
9.4
通讯作者：
Woodson, Jesse D.
中科院分区：
文献类型：
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作者：
Alamdari, Kamran;Fisher, Karen E.;Woodson, Jesse D.
活性氧（Reactive oxygen species， ROS）在叶绿体中产生，不仅引起氧化损伤，而且启动叶绿体质量控制途径、细胞死亡和基因表达。拟南芥质体铁螯合酶2 （fc2）突变体在叶绿体中产生ROS单线态氧，激活这些信号通路，但其机制在很大程度上是未知的。在这里，我们描述了一个fc2抑制突变，并将其定位于CYTIDINE TRIPHOSPHATE SYNTHASE TWO (CTPS2)，该基因编码拟南芥中5种酶中的一种，这些酶是重新合成细胞质CTP（和dCTP）所必需的。ctps2突变减少了叶绿体转录物和DNA含量，但没有类似地影响线粒体。外源性给食dCTP前体脱氧胞苷可以恢复叶绿体核酸含量和单线态氧信号，这表明ctps2通过限制核苷酸来阻断叶绿体基因组维持的信号传导。对芸苔科植物CTPS同源物的研究表明，CTPS2是一个不同于CTPS3的古老谱系的成员。互补研究证实了这一分析；CTPS3无法弥补CTPS2在提供叶绿体DNA核苷酸和信号传导方面的功能。我们的研究将细胞质核苷酸代谢与叶绿体质量控制途径联系起来。这种连接是由一个保守的CTPS酶分支实现的，该分支为叶绿体功能提供核苷酸，从而允许应激信号发生。
Reactive oxygen species (ROS) produced in chloroplasts cause oxidative damage, but also signal to initiate chloroplast quality control pathways, cell death, and gene expression. The Arabidopsis thaliana plastid ferrochelatase two (fc2) mutant produces the ROS singlet oxygen in chloroplasts that activates such signaling pathways, but the mechanisms are largely unknown. Here we characterize one fc2 suppressor mutation and map it to CYTIDINE TRIPHOSPHATE SYNTHASE TWO (CTPS2), which encodes one of five enzymes in Arabidopsis necessary for de novo cytoplasmic CTP (and dCTP) synthesis. The ctps2 mutation reduces chloroplast transcripts and DNA content without similarly affecting mitochondria. Chloroplast nucleic acid content and singlet oxygen signaling are restored by exogenous feeding of the dCTP precursor deoxycytidine, suggesting ctps2 blocks signaling by limiting nucleotides for chloroplast genome maintenance. An investigation of CTPS orthologs in Brassicaceae showed CTPS2 is a member of an ancient lineage distinct from CTPS3. Complementation studies confirmed this analysis; CTPS3 was unable to compensate for CTPS2 function in providing nucleotides for chloroplast DNA and signaling. Our studies link cytoplasmic nucleotide metabolism with chloroplast quality control pathways. Such a connection is achieved by a conserved clade of CTPS enzymes that provide nucleotides for chloroplast function, thereby allowing stress signaling to occur.