LCAA, a Novel Factor Required for Magnesium Protoporphyrin Monomethylester Cyclase Accumulation and Feedback Control of Aminolevulinic Acid Biosynthesis in Tobacco
LCAA, a Novel Factor Required for Magnesium Protoporphyrin Monomethylester Cyclase Accumulation and Feedback Control of Aminolevulinic Acid Biosynthesis in Tobacco
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DOI：
10.1104/pp.112.206045
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发表时间：
2012-12-01
期刊：
影响因子：
7.4
通讯作者：
Schoettler, Mark Aurel
中科院分区：
文献类型：
--
作者：
Albus, Christin Anne;Salinas, Annabel;Schoettler, Mark Aurel
从筛选部分下调导致烟草（Nicotiana tabacum）中强烈叶绿素缺乏的基因中获得低叶绿素积累A（LCAA）反义植物。LCAA突变体受到功能未知的质体定位蛋白质的影响，该蛋白质在蓝细菌和所有光合真核生物中是保守的。它们遭受急剧减少的捕光复合物（LHC）的内容，而每叶面积的所有其他光合复合物的积累受到的影响较小。由于LHC蛋白质的干扰积累可能归因于LHC生物合成本身的缺陷或叶绿素生物合成的瓶颈，因此测量了叶绿素合成速率和叶绿素合成中间体。LCAA反义植物积累镁（Mg）原卟啉单甲酯并且含有降低的原叶绿素水平和降低的CHL 27（Mg原卟啉单甲酯环化酶的亚基）含量。双分子荧光互补分析证实LCAA和CHL 27之间的直接相互作用。5-氨基乙酰丙酸合成速率增加，并与谷氨酰转移RNA还原酶含量增加相关。我们认为LCAA编码镁原卟啉单甲酯环化酶的另一个亚基，是CHL 27稳定所需的，并有助于5-氨基乙酰丙酸生物合成（叶绿素生物合成的限速步骤）的反馈控制。
Low Chlorophyll Accumulation A (LCAA) antisense plants were obtained from a screen for genes whose partial down-regulation results in a strong chlorophyll deficiency in tobacco (Nicotiana tabacum). The LCAA mutants are affected in a plastid-localized protein of unknown function, which is conserved in cyanobacteria and all photosynthetic eukaryotes. They suffer from drastically reduced light-harvesting complex (LHC) contents, while the accumulation of all other photosynthetic complexes per leaf area is less affected. As the disturbed accumulation of LHC proteins could be either attributable to a defect in LHC biogenesis itself or to a bottleneck in chlorophyll biosynthesis, chlorophyll synthesis rates and chlorophyll synthesis intermediates were measured. LCAA antisense plants accumulate magnesium (Mg) protoporphyrin monomethylester and contain reduced protochlorophyllide levels and a reduced content of CHL27, a subunit of the Mg protoporphyrin monomethylester cyclase. Bimolecular fluorescence complementation assays confirm a direct interaction between LCAA and CHL27. 5-Aminolevulinic acid synthesis rates are increased and correlate with an increased content of glutamyl-transfer RNA reductase. We suggest that LCAA encodes an additional subunit of the Mg protoporphyrin monomethylester cyclase, is required for the stability of CHL27, and contributes to feedback-control of 5-aminolevulinic acid biosynthesis, the rate-limiting step of chlorophyll biosynthesis.