Chloroplastic thioredoxin m functions as a major regulator of Calvin cycle enzymes during photosynthesis in vivo
Chloroplastic thioredoxin m functions as a major regulator of Calvin cycle enzymes during photosynthesis in vivo
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DOI：
10.1111/tpj.13049
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发表时间：
2015-12-01
期刊：
影响因子：
7.2
通讯作者：
Motohashi, Ken
中科院分区：
文献类型：
--
作者：
Okegawa, Yuki;Motohashi, Ken
硫氧还蛋白（Trxs）以光依赖的方式调节各种叶绿体蛋白的活性。五种类型的Trxs在拟南芥叶绿体不同的生理过程中发挥作用。先前的体外实验已经表明f型Trx（Trx f）是叶绿体酶（包括卡尔文循环酶）的主要氧化还原调节剂。为了研究每种Trx同种型对氧化还原调节系统的体内贡献，我们首先定量了叶绿体基质中每种Trx同种型的蛋白质浓度。m型Trx（Trx m）由四种亚型组成，是最丰富的类型。接下来，我们分析了几个拟南芥Trx-m缺陷突变体，以阐明Trx m在体内的生理作用。缺乏Trx m会损害植物生长，降低CO2同化速率。我们还确定了Trx靶酶的氧化还原状态，以检查它们的光还原，这是酶活化所必需的。在Trx-m缺陷突变体中，果糖-1，6-二磷酸酶和景天庚酮糖-1，7-二磷酸酶的降低水平低于野生型。与历史观点不一致的是，我们的体内研究表明，Trx m在卡尔文循环酶的激活中起着比Trx f更重要的作用。
Thioredoxins (Trxs) regulate the activity of various chloroplastic proteins in a light-dependent manner. Five types of Trxs function in different physiological processes in the chloroplast of Arabidopsis thaliana. Previous in vitro experiments have suggested that the f-type Trx (Trx f) is the main redox regulator of chloroplast enzymes, including Calvin cycle enzymes. To investigate the in vivo contribution of each Trx isoform to the redox regulatory system, we first quantified the protein concentration of each Trx isoform in the chloroplast stroma. The m-type Trx (Trx m), which consists of four isoforms, was the most abundant type. Next, we analyzed several Arabidopsis Trx-m-deficient mutants to elucidate the physiological role of Trx m in vivo. Deficiency of Trx m impaired plant growth and decreased the CO2 assimilation rate. We also determined the redox state of Trx target enzymes to examine their photo-reduction, which is essential for enzyme activation. In the Trx-m-deficient mutants, the reduction level of fructose-1,6-bisphosphatase and sedoheptulose-1,7-bisphosphatase was lower than that in the wild type. Inconsistently with the historical view, our in vivo study suggested that Trx m plays a more important role than Trx f in the activation of Calvin cycle enzymes.