Identification of Arabidopsis VTC3 as a putative and unique dual function protein kinase::protein phosphatase involved in the regulation of the ascorbic acid pool in plants
Identification of Arabidopsis VTC3 as a putative and unique dual function protein kinase::protein phosphatase involved in the regulation of the ascorbic acid pool in plants
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DOI：
10.1093/jxb/ert140
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发表时间：
2013-07-01
影响因子：
6.9
通讯作者：
Buckenmeyer, Gail
中科院分区：
文献类型：
--
作者：
Conklin, Patricia L.;DePaolo, Dennis;Buckenmeyer, Gail
抗坏血酸（阿萨）在植物中以高水平存在，并且是有效的抗氧化剂和细胞还原剂。植物阿萨的主要生物合成途径是通过中间体d-甘露糖和l-半乳糖。虽然有充分的证据表明，植物响应波动的环境条件与池的大小变化的阿萨，目前还不清楚这种调节是如何发生的。AsA缺陷型拟南芥突变体vtc 3 -1和vtc 3 -2定义了一个基因座，该基因座已通过定位克隆鉴定为At 2g 40860。通过AsA缺陷型At 2g 40860插入突变体的研究以及通过用野生型At 2g 40860 cDNA对vtc 3 -1和vtc 3 -2中的阿萨缺陷进行转基因互补来确认该鉴定。预测非常不寻常的VTC 3基因编码一种新的多肽，其N-末端蛋白激酶结构域共价连接到C-末端蛋白磷酸酶2C型结构域。该基因的同源物仅存在于绿色植物纲/叶绿体纲中，因此该基因可能沿着d-甘露糖/l-半乳糖阿萨生物合成途径。vtc 3突变体植物在响应光和热而提高阿萨库的能力方面是有缺陷的，这表明VTC 3在调节阿萨库大小中具有重要作用。
Ascorbic acid (AsA) is present at high levels in plants and is a potent antioxidant and cellular reductant. The major plant AsA biosynthetic pathway is through the intermediates d-mannose and l-galactose. Although there is ample evidence that plants respond to fluctuating environmental conditions with changes in the pool size of AsA, it is unclear how this regulation occurs. The AsA-deficient Arabidopsis thaliana mutants vtc3-1 and vtc3-2 define a locus that has been identified by positional cloning as At2g40860. Confirmation of this identification was through the study of AsA-deficient At2g40860 insertion mutants and by transgenic complementation of the AsA deficiency in vtc3-1 and vtc3-2 with wild-type At2g40860 cDNA. The very unusual VTC3 gene is predicted to encode a novel polypeptide with an N-terminal protein kinase domain tethered covalently to a C-terminal protein phosphatase type 2C domain. Homologues of this gene exist only within the Viridiplantae/Chloroplastida and the gene may therefore have arisen along with the d-mannose/l-galactose AsA biosynthetic pathway. The vtc3 mutant plants are defective in the ability to elevate the AsA pool in response to light and heat, suggestive of an important role for VTC3 in the regulation of the AsA pool size.