The conservative cysteines in transmembrane domain of AtVKOR/LTO1 are critical for photosynthetic growth and photosystem II activity in Arabidopsis.
The conservative cysteines in transmembrane domain of AtVKOR/LTO1 are critical for photosynthetic growth and photosystem II activity in Arabidopsis.
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DOI：
10.3389/fpls.2015.00238
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发表时间：
2015
影响因子：
5.6
通讯作者：
Wang XY
中科院分区：
文献类型：
--
作者：
Du JJ;Zhan CY;Lu Y;Cui HR;Wang XY
类囊体蛋白维生素 K 环氧化物还原酶 (AtVKOR/LTO1) 参与氧化还原。这种化合物的缺乏会导致拟南芥出现多效性缺陷，例如生长严重发育迟缓、叶子变小和开花延迟。野生型 AtVKOR (VKORWT) 与 vkor 突变株系的转基因互补最终证明表型变化是由该基因引起的。然而，AtVKOR 是否通过其蛋白质氧化还原在拟南芥中发挥作用尚不清楚。为了进一步研究 AtVKOR 体内氧化还原活性位点，构建了一系列含有半胱氨酸突变体 VKOR 的质粒，并将其转化到 vkor 缺陷系中。与转基因AtVKORWT植物相比，具有单个保守半胱氨酸突变（VKORC109A、VKORC116A、VKORC195A和VKORC198A）的转基因植物的大小较小，并且两个双半胱氨酸突变（VKORC109AC116A和VKORC195AC198A）表现出明显的生长迟缓，与vkor突变系相似。然而，两个非保守半胱氨酸（VKORC46A和VKORC230A）的突变对拟南芥的表型没有表现出明显的变化。一致地，在正常生长光和高光下，双半胱氨酸突变植物中光系统II（PSII）的最大和实际效率显着降低至与vkor突变系相似的水平。在高光下的两个双半胱氨酸突变中观察到 D1 蛋白量显着减少和活性氧积累增加。以上结果表明，跨膜结构域保守的半胱氨酸是拟南芥AtVKOR的功能位点，AtVKOR的氧化还原酶活性与拟南芥自养光合生长和PSII活性直接相关。
Thylakoid protein vitamin K epoxide reductase (AtVKOR/LTO1) is involved in oxidoreduction. The deficiency of this compound causes pleiotropic defects in Arabidopsis thaliana, such as severely stunted growth, smaller sized leaves, and delay of flowering. Transgenic complementation of wild-type AtVKOR (VKORWT) to vkor mutant lines ultimately demonstrates that the phenotype changes are due to this gene. However, whether AtVKOR functions in Arabidopsis through its protein oxidoreduction is unknown. To further study the redox-active sites of AtVKOR in vivo, a series of plasmids containing cysteine-mutant VKORs were constructed and transformed into vkor deficient lines. Compared with transgenic AtVKORWT plants, the size of the transgenic plants with a single conservative cysteine mutation (VKORC109A, VKORC116A, VKORC195A, and VKORC198A) were smaller, and two double-cysteine mutations (VKORC109AC116A and VKORC195AC198A) showed significantly stunted growth, similar with the vkor mutant line. However, mutations of two non-conservative cysteines (VKORC46A and VKORC230A) displayed little obvious changes in the phenotypes of Arabidopsis. Consistently, the maximum and actual efficiency of photosystem II (PSII) in double-cysteine mutation plants decreased significantly to the level similar to that of the vkor mutant line both under normal growth light and high light. A significantly decreased amount of D1 protein and increased accumulation of reactive oxygen species were observed in two double-cysteine mutations under high light. All of the results above indicated that the conservative cysteines in transmembrane domains were the functional sites of AtVKOR in Arabidopsis and that the oxidoreductase activities of AtVKOR were directly related to the autotrophic photosynthetic growth and PSII activity of Arabidopsis thaliana.
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