Chlorophyll Synthase under Epigenetic Surveillance Is Critical for Vitamin E Synthesis, and Altered Expression Affects Tocopherol Levels in Arabidopsis
Chlorophyll Synthase under Epigenetic Surveillance Is Critical for Vitamin E Synthesis, and Altered Expression Affects Tocopherol Levels in Arabidopsis
复制标题
表观遗传监控下的叶绿素合酶对于维生素 E 合成至关重要，表达改变会影响拟南芥中的生育酚水平
DOI：
10.1104/pp.15.00594
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发表时间：
2015-08-01
期刊：
影响因子：
7.4
通讯作者：
Cahoon, Edgar B.
中科院分区：
文献类型：
--
作者：
Zhang, Chunyu;Zhang, Wei;Cahoon, Edgar B.
叶绿素合成酶催化叶绿素生物合成的最后一步：叶绿素与香叶基香叶基二磷酸或植基二磷酸（PDP）的酯化反应。最近的研究指出，香叶基香叶基还原酶参与香叶基的叶绿素相关还原是合成生育酚的PDP前体的主要途径。这种PDP合成的间接途径表明叶绿素合成酶在生育酚生产中的关键作用，以产生香叶基香叶基-叶绿素底物香叶基香叶基还原酶。在这项研究中，叶绿素合成酶的贡献生育酚形成在拟南芥（拟南芥），探讨了破坏和改变相应的基因叶绿素合成酶（CHLSYN; At 3g 51820）的表达。来自纯合的chlysyn 1 -1无效突变体的叶几乎不含生育酚，而种子仅含有约25%的野生型生育酚水平。叶片的RNA干扰线与部分抑制CHLSYN显示显着减少叶绿素，但高达2倍的生育酚浓度增加。花椰菜花叶病毒35 S介导的CHLSYN过表达意外地导致了高频率的共抑制表型，伴随着强烈降低的叶绿素含量和增加的生育酚水平。这种表型和CHLSYN衍生的小干扰RNA的相关检测与CHLSYN在RNA定向RNA聚合酶6（rdr 6）中的过表达逆转，rdr 6在RNA依赖性RNA聚合酶6中有缺陷，RNA依赖性RNA聚合酶6是有义转基因诱导的小干扰RNA产生的关键酶。在rdr 6中CHLSYN过表达对叶绿素含量几乎没有影响，但导致叶片中生育酚水平降低高达30%。这些发现表明，改变的CHLSYN表达影响生育酚水平，并且还表明CHLSYN控制叶绿素和生育酚合成的强表观遗传监视。
Chlorophyll synthase catalyzes the final step in chlorophyll biosynthesis: the esterification of chlorophyllide with either geranylgeranyl diphosphate or phytyl diphosphate (PDP). Recent studies have pointed to the involvement of chlorophyll-linked reduction of geranylgeranyl by geranylgeranyl reductase as a major pathway for the synthesis of the PDP precursor of tocopherols. This indirect pathway of PDP synthesis suggests a key role of chlorophyll synthase in tocopherol production to generate the geranylgeranyl-chlorophyll substrate for geranylgeranyl reductase. In this study, contributions of chlorophyll synthase to tocopherol formation in Arabidopsis (Arabidopsis thaliana) were explored by disrupting and altering expression of the corresponding gene CHLOROPHYLL SYNTHASE (CHLSYN; At3g51820). Leaves from the homozygous chlysyn1-1 null mutant were nearly devoid of tocopherols, whereas seeds contained only approximately 25% of wild-type tocopherol levels. Leaves of RNA interference lines with partial suppression of CHLSYN displayed marked reductions in chlorophyll but up to a 2-fold increase in tocopherol concentrations. Cauliflower mosaic virus35S-mediated overexpression of CHLSYN unexpectedly caused a cosuppression phenotype at high frequencies accompanied by strongly reduced chlorophyll content and increased tocopherol levels. This phenotype and the associated detection of CHLSYN-derived small interfering RNAs were reversed with CHLSYN overexpression in rna-directed rna polymerase6 (rdr6), which is defective in RNA-dependent RNA polymerase6, a key enzyme in sense transgene-induced small interfering RNA production. CHLSYN overexpression in rdr6 had little effect on chlorophyll content but resulted in up to a 30% reduction in tocopherol levels in leaves. These findings show that altered CHLSYN expression impacts tocopherol levels and also, show a strong epigenetic surveillance of CHLSYN to control chlorophyll and tocopherol synthesis.