Two short-chain dehydrogenase/reductases, NON-YELLOW COLORING 1 and NYC1-LIKE, are required for chlorophyll b and light-harvesting complex II degradation during senescence in rice
Two short-chain dehydrogenase/reductases, NON-YELLOW COLORING 1 and NYC1-LIKE, are required for chlorophyll b and light-harvesting complex II degradation during senescence in rice
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DOI：
10.1111/j.1365-313x.2008.03670.x
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发表时间：
2009-01-01
期刊：
影响因子：
7.2
通讯作者：
Kusaba, Makoto
中科院分区：
文献类型：
--
作者：
Sato, Yutaka;Morita, Ryouhei;Kusaba, Makoto
黄化是叶片衰老过程中的一个显著现象，它与叶绿素和叶绿素-蛋白质复合体的降解有关。水稻中的非黄色COLORING1(NYC1)编码一种膜定位的短链脱氢酶/还原酶(SDR)，被认为是一种催化叶绿素b降解第一步所必需的叶绿素b还原酶。对NYC1突变体的分析表明，在叶片衰老过程中，叶绿素b的降解是捕光复合体II和类囊体粒的降解所必需的。系统发育分析进一步揭示了NYC1样蛋白(NOL)的存在，它是与NYC1关系最密切的蛋白。本文还发现，在水稻中，nol突变体表现出与nyc1突变体非常相似的保绿表型，即在衰老过程中，叶绿素b的降解受到严重抑制，捕光复合体II被选择性地保留，导致即使在衰老后期也能保留类囊体基粒。NYC1nol双突变体对叶绿素降解的抑制作用没有明显增强。尽管缺少跨膜区，NOL仍定位于类囊体膜的基质侧。免疫沉淀分析表明，NOL和NYC1在体外存在物理相互作用。这些观察结果表明，NOL和NYC1共同定位于水稻的类囊体膜上，并以复合体的形式在水稻中作为叶绿素b还原酶发挥作用。
Yellowing, which is related to the degradation of chlorophyll and chlorophyll-protein complexes, is a notable phenomenon during leaf senescence. NON-YELLOW COLORING1 (NYC1) in rice encodes a membrane-localized short-chain dehydrogenase/reductase (SDR) that is thought to represent a chlorophyll b reductase necessary for catalyzing the first step of chlorophyll b degradation. Analysis of the nyc1 mutant, which shows the stay-green phenotype, revealed that chlorophyll b degradation is required for the degradation of light-harvesting complex II and thylakoid grana in leaf senescence. Phylogenetic analysis further revealed the existence of NYC1-LIKE (NOL) as the most closely related protein to NYC1. In the present paper, the nol mutant in rice was also found to show a stay-green phenotype very similar to that of the nyc1 mutant, i.e. the degradation of chlorophyll b was severely inhibited and light-harvesting complex II was selectively retained during senescence, resulting in the retention of thylakoid grana even at a late stage of senescence. The nyc1 nol double mutant did not show prominent enhancement of inhibition of chlorophyll degradation. NOL was localized on the stromal side of the thylakoid membrane despite the lack of a transmembrane domain. Immunoprecipitation analysis revealed that NOL and NYC1 interact physically in vitro. These observations suggest that NOL and NYC1 are co-localized in the thylakoid membrane and act in the form of a complex as a chlorophyll b reductase in rice.