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>Arabidopsis S-Sulfocysteine Synthase Activity Is Essential for Chloroplast Function and Long-Day Light-Dependent Redox Control
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Arabidopsis S-Sulfocysteine Synthase Activity Is Essential for Chloroplast Function and Long-Day Light-Dependent Redox Control
n nnnIn bacteria, the biosynthesis of Cys is accomplished by twoenzymes that are encoded by the cysK and cysM genes. CysM isalso able to use thiosulfate as a substrate to produce S-sulfocysteine.In plant cells, the biosynthesis of Cys occurs in the cytosol,mitochondria, and chloroplasts. Chloroplasts contain two O-acetylserine(thiol)lyasehomologs, which are encoded by the OAS-B and CS26 genes in Arabidopsisthaliana. An in vitro enzymatic analysis of the recombinantCS26 protein demonstrated that this isoform possesses S-sulfocysteinesynthase activity and lacks O-acetylserine(thiol)lyase activity.In vivo functional analysis of this enzyme in knockout mutantsdemonstrated that mutation of CS26 suppressed the S-sulfocysteinesynthase activity that was detected in the wild type; furthermore,the cs26 mutants exhibited a reduction in size and showed paleness,but penetrance of the growth phenotype depended on the lightregime. The cs26 mutant plants also had reductions in chlorophyllcontent and photosynthetic activity (neither of which were observedin oas-b mutants) as well as elevated glutathione levels. However,cs26 leaves were not able to properly detoxify reactive oxygenspecies, which accumulated to high levels under long-day growthconditions. The transcriptional profile of the cs26 mutant revealedthat the mutation had a pleiotropic effect on many cellularand metabolic processes. Our findings reveal that S-sulfocysteineand the activity of S-sulfocysteine synthase play importantroles in chloroplast function and are essential for light-dependentredox regulation within the chloroplast.展开▼
机译:ABSTRACTn FONT> TH> TR> TABLE> n
n TOP n <字体颜色= 464c53>抽象 FONT> n 介绍 n 结果 n 讨论 n 方法 n 参考文献 n FONT> TH> TR> TABLE> n nnnIn细菌中,Cys的生物合成是通过两种 SUP>酶完成的是由 cysK I>和 cysM I>基因编码的。 CysM是 SUP>,也可以使用硫代硫酸盐作为底物来产生 S I>-磺基半胱氨酸。 SUP>在植物细胞中,Cys的生物合成发生在细胞质中, SUP>线粒体和叶绿体。叶绿体含有两个 O I>-乙酰丝氨酸(硫醇)裂解酶 SUP>同源物,它们由 OAS-B I>和 CS26 I>编码拟南芥 SUP>拟南芥 I>中的基因。重组 SUP> CS26蛋白的体外酶促分析表明,该同工型具有 S I>-磺基半胱氨酸 SUP>合酶活性,但缺乏 O I >-乙酰丝氨酸(硫醇)裂解酶活性。 SUP>该酶在敲除突变体 SUP>中的体内功能分析表明, CS26 I>的突变抑制了在野生型中检测到的S I>-硫代半胱氨酸 SUP>合酶活性;此外, SUP> cs26 I>突变体的大小减小并显示出苍白, SUP>,但生长表型的穿透性取决于光 SUP>政权。 cs26 I>突变植物的叶绿素 SUP>含量和光合活性也降低(在 oas-b I中均未观察到 SUP>) >突变体)以及谷胱甘肽水平升高。但是, SUP> cs26 I>叶片不能适当地解毒活性氧 SUP>,这些氧在长期生长下积累到很高的水平 SUP>条件。 cs26 I>突变体的转录谱表明, SUP>表明该突变对许多细胞 SUP>和代谢过程具有多效作用。我们的发现表明 S I>-硫代半胱氨酸 SUP>和 S I>-硫代半胱氨酸合酶的活性在叶绿体功能中起重要的 SUP>角色对叶绿体中依赖光的 SUP>氧化还原调节至关重要。 SUP>
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