Functional analysis of isoforms of NADPH:protochlorophyllide oxidoreductase (POR), PORB and PORC, in Arabidopsis thaliana
Functional analysis of isoforms of NADPH:protochlorophyllide oxidoreductase (POR), PORB and PORC, in Arabidopsis thaliana
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DOI：
10.1093/pcp/pcg128
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发表时间：
2003-10-01
影响因子：
4.9
通讯作者：
Takamiya, K
中科院分区：
文献类型：
--
作者：
Masuda, T;Fusada, N;Takamiya, K
NADPH：原叶绿素内酯氧化还原酶 (POR) 催化原叶绿素内酯的光依赖性还原。为了阐明拟南芥中三种差异调节的 POR 亚型（PORA、PORB 和 PORC）的生理功能，我们分离了 porB 和 porC 的 T-DNA 标记无效突变体。突变体的成熟幼苗具有正常的光合能力，表明 PORB 和 PORC 在发育的植物中是可互换的且功能冗余。在黄化幼苗中，只有porB表现出光活性原叶绿素内酯和原片层体(PLB)尺寸的减少，表明PORB以及PORA在黄化幼苗中的PLB组装和光活性原叶绿素内酯形成中发挥作用。当光照时，黄化的porB幼苗能够达到与野生型相似的程度的绿化，而在弱光条件下绿化显着减少。绿化过程中，强光照射增加了PORC蛋白的水平，而高光条件下porC的绿化受到抑制。 porB（而非 porC）黄化幼苗比野生型对远红绿化块更敏感，这是由内源性 POR 蛋白耗尽导致光氧化损伤引起的。这些结果表明，在绿化开始时，PLB 对于在各种光照条件下有效捕获光能进行光转换非常重要，而强光照射诱导的 PORC 有助于黄化幼苗绿化过程中的光保护。
NADPH:protochlorophyllide oxidoreductase (POR) catalyzes the light-dependent reduction of protochlorophyllide. To elucidate the physiological function of three differentially regulated POR isoforms (PORA, PORB and PORC) in Arabidopsis thaliana, we isolated T-DNA tagged null mutants of porB and porC. The mature seedlings of the mutants had normal photosynthetic competencies, showing that PORB and PORC are interchangeable and functionally redundant in developed plants. In etiolated seedlings, only porB showed a reduction in the photoactive protochlorophyllide and the size of prolamellar bodies (PLBs), indicating that PORB, as well as PORA, functioned in PLB assembly and photoactive protochlorophyllide formation in etiolated seedlings. When illuminated, the etiolated porB seedling was able to green to a similar extent as the wild type, whereas the greening was significantly reduced under low light conditions. During greening, high light irradiation increased the level of PORC protein, and the greening of porC was repressed under high light conditions. The porB, but not porC, etiolated seedling was more sensitive to the far-red block of greening than the wild type, which is caused by depletion of endogenous POR proteins resulting in photo-oxidative damage. These results suggest that, at the onset of greening, PLBs are important for efficient capture of light energy for photoconversion under various light conditions, and PORC, which is induced by high light irradiation, contributes to photoprotection during greening of the etiolated seedlings.