Rice NON-YELLOW COLORING1 is involved in light-harvesting complex II and grana degradation during leaf senescence
Rice NON-YELLOW COLORING1 is involved in light-harvesting complex II and grana degradation during leaf senescence
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DOI：
10.1105/tpc.106.042911
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发表时间：
2007-04-01
期刊：
影响因子：
11.6
通讯作者：
Tanaka, Ayumi
中科院分区：
文献类型：
--
作者：
Kusaba, Makoto;Ito, Hisashi;Tanaka, Ayumi
叶绿素降解是叶片衰老的一个方面，这是一个积极的过程，以挽救营养物质从老组织。non-yellow coloring1 （nyc1）是水稻（Oryza sativa）中一种在衰老过程中叶绿素降解受损的保持绿色突变体。色素分析表明，nyc1不仅抑制了叶绿素的降解，而且抑制了LHCII结合的类胡萝卜素的降解，其中大部分LHCII亚型在衰老过程中被选择性保留。对nyc1叶绿体的超微结构分析显示，即使在衰老后期也存在大而厚的颗粒，这表明LHCII的降解是类囊体膜适当退化的必要条件。NYC1基因的图谱克隆表明，它编码一个叶绿体定位的短链脱氢酶/还原酶（SDR），具有3个跨膜结构域。NYC1蛋白的预测结构和NYC1突变体的表型表明NYC1可能是叶绿素b还原酶。虽然我们无法检测到NYC1的叶绿素b还原酶活性，但水稻中与NYC1密切相关的蛋白质NOL （NYC1-like）在体外显示出叶绿素b还原酶活性。我们认为NYC1和NOL编码的叶绿素b还原酶具有不同的功能。我们的数据共同表明，鉴定的SDR蛋白NYC1在衰老过程中调控LHCII和类囊体膜降解中起重要作用。
Chlorophyll degradation is an aspect of leaf senescence, which is an active process to salvage nutrients from old tissues. non-yellow coloring1 (nyc1) is a rice (Oryza sativa) stay-green mutant in which chlorophyll degradation during senescence is impaired. Pigment analysis revealed that degradation of not only chlorophylls but also light-harvesting complex II (LHCII) bound carotenoids was repressed in nyc1, in which most LHCII isoforms were selectively retained during senescence. Ultrastructural analysis of nyc1 chloroplasts revealed that large and thick grana were present even in the late stage of senescence, suggesting that degradation of LHCII is required for the proper degeneration of thylakoid membranes. Map-based cloning of NYC1 revealed that it encodes a chloroplast-localized short-chain dehydrogenase/reductase (SDR) with three transmembrane domains. The predicted structure of the NYC1 protein and the phenotype of the nyc1 mutant suggest the possibility that NYC1 is a chlorophyll b reductase. Although we were unable to detect the chlorophyll b reductase activity of NYC1, NOL (for NYC1-like), a protein closely related to NYC1 in rice, showed chlorophyll b reductase activity in vitro. We suggest that NYC1 and NOL encode chlorophyll b reductases with divergent functions. Our data collectively suggest that the identified SDR protein NYC1 plays essential roles in the regulation of LHCII and thylakoid membrane degradation during senescence.