Identification of a Chlorophyll Dephytylase Involved in Chlorophyll Turnover in Arabidopsis
Identification of a Chlorophyll Dephytylase Involved in Chlorophyll Turnover in Arabidopsis
复制标题
DOI：
10.1105/tpc.16.00478
复制
发表时间：
2016-12-01
期刊：
影响因子：
11.6
通讯作者：
Charng, Yee-yung
中科院分区：
文献类型：
--
作者：
Lin, Yao-Pin;Wu, Meng-Chen;Charng, Yee-yung
叶绿素在光系统修复过程中在绿色器官中翻转，并通过去植基化和再植基化被挽救，但参与去植基化的酶尚不清楚。我们已经确定了一个拟南芥类囊体蛋白与一个假定的水解酶结构域，可以在体外和体内脱叶绿素。相应的基因座，叶绿素DEPHYTYLASE 1（CLD 1），通过定位一个半显性，热敏，错义等位基因（cld 1 -1）。CLD 1在产氧光合生物中是保守的，与在叶片衰老期间叶绿素分解中起作用的脱镁叶绿素酶共享结构相似性。与脱镁叶绿素酶不同，CLD 1主要在绿色器官中表达，并且可以在体外使叶绿素脱镁。由cld 1 -1编码的突变蛋白的比活性显著高于野生型酶，这与cld 1 -1突变的半显性性质一致。超最佳的CLD 1的活动在cld 1 -1突变体和转基因幼苗导致叶绿素脱植基热休克后，这导致光依赖性子叶漂白衍生的叶绿素类化合物的比例积累。减少CLD 1表达降低耐热性和光系统II的光化学效率在长时间的中度热胁迫。两者合计，我们的研究结果表明，CLD 1是长期寻求的酶，用于在叶绿体内的稳态营业额期间从叶绿素中去除叶绿醇链。
Chlorophyll turns over in green organs during photosystem repair and is salvaged via de- and rephytylation, but the enzyme involved in dephytylation is unknown. We have identified an Arabidopsis thaliana thylakoid protein with a putative hydrolase domain that can dephytylate chlorophyll in vitro and in vivo. The corresponding locus, CHLOROPHYLL DEPHYTYLASE1 (CLD1), was identified by mapping a semidominant, heat-sensitive, missense allele (cld1-1). CLD1 is conserved in oxygenic photosynthetic organisms, sharing structural similarity with pheophytinase, which functions in chlorophyll breakdown during leaf senescence. Unlike pheophytinase, CLD1 is predominantly expressed in green organs and can dephytylate chlorophyll in vitro. The specific activity is significantly higher for the mutant protein encoded by cld1-1 than the wild-type enzyme, consistent with the semidominant nature of the cld1-1 mutation. Supraoptimal CLD1 activities in cld1-1 mutants and transgenic seedlings led to the proportional accumulation of chlorophyllides derived from chlorophyll dephytylation after heat shock, which resulted in light-dependent cotyledon bleaching. Reducing CLD1 expression diminished thermotolerance and the photochemical efficiency of photosystem II under prolonged moderate heat stress. Taken together, our results suggest that CLD1 is the long-sought enzyme for removing the phytol chain from chlorophyll during its turnover at steady state within the chloroplast.