Genetic analysis of chlorophyll synthesis and degradation regulated by BALANCE of CHLOROPHYLL METABOLISM
Genetic analysis of chlorophyll synthesis and degradation regulated by BALANCE of CHLOROPHYLL METABOLISM
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叶绿素代谢平衡调节叶绿素合成和降解的遗传分析
DOI：
10.1093/plphys/kiac059
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发表时间：
2022
期刊：
影响因子：
7.4
通讯作者：
Kusaba Makoto
中科院分区：
文献类型：
--
作者：
Yamatani Hiroshi;Ito Takeshi;Nishimura Kenji;Yamada Tetsuya;Sakamoto Wataru;Kusaba Makoto
叶绿素（Chl）作为光系统超配合物的一个组成部分，具有捕获和转换光能的许多基本功能。叶绿素在叶片衰老过程中的降解也是叶绿体充分退化和从衰老叶片中回收营养物质所必需的。本研究对拟南芥（Arabidopsis thaliana）中通过调节Chl的合成和降解来控制Chl水平的叶绿素代谢ism1 （BCM1）和BCM2，以及编码mg脱羧酶并催化Chl降解的STAY-GREEN (SGR)1（也称为NON-YELLOWING1 [NYE1]）和SGR2的平衡功能进行了遗传分析。对BCM1和BCM2的分析表明，BCM1和BCM2都参与了存在叶片中Chl水平的调控和衰老叶片中Chl降解的调控。对bcm1、bcm2、nye1、nye2的分析表明，BCMs通过调控SGR活性，抑制存在叶和衰老叶的chl降解活性。此外，转激活分析和染色质免疫沉淀（ChIP）实验显示，GOLDEN2-LIKE1 (GLK1)，一个调节光系统相关蛋白（如光收集Chl a/b结合蛋白（LHCPs））编码基因表达的中心转录因子，直接调控bcm1的转录。LHCP通过与Chl结合而稳定，这表明GLKs通过bcm介导的Chl水平调控，通过转录和翻译后调控来控制LHCP的数量。同时，我们通过基因组编辑在莴苣（Lactuca sativa）中产生了bcmortholog突变体，发现其表现出早期黄化表型，但在存在叶片中Chl含量略有降低。因此，本研究揭示了糖尿病患者通过GLK-BCM途径对Chl和LHCP水平的保守但略微多样化的调节。
Chlorophyll (Chl) serves a number of essential functions, capturing and converting light energy as a component of photosystem supercomplexes. Chl degradation during leaf senescence is also required for adequate degeneration of chloroplasts and salvaging of nutrients from senescent leaves. In this study, we performed genetic analysis to determine the functions of BALANCE of CHLOROPHYLL METABOLISM1 (BCM1) and BCM2, which control Chl levels by regulating synthesis and degradation, and STAY-GREEN (SGR)1 (also known as NON-YELLOWING1 [NYE1]) and SGR2, which encode Mg-dechelatase and catalyze Chladegradation in Arabidopsis (Arabidopsis thaliana). Analysis ofbcm1 bcm2revealed that both BCM1 and BCM2 are involved in the regulation of Chl levels in presenescent leaves and Chl degradation in senescing leaves. Analysis ofbcm1 bcm2 nye1 nye2suggested that BCMs repress Chl-degrading activity in both presenescent and senescing leaves by regulating SGR activity. Furthermore, transactivation analysis and chromatin immunoprecipitation (ChIP) assay revealed that GOLDEN2-LIKE1 (GLK1), a central transcription factor regulating the expression of genes encoding photosystem-related proteins, such as light-harvesting Chl a/b-binding proteins (LHCPs), directly regulates the transcription ofBCM1. LHCPs are stabilized by Chl binding, suggesting that GLKs control the amount of LHCP through transcriptional and post-translational regulation via BCM-mediated Chl-level regulation. Meanwhile, we generated a mutant of theBCMortholog in lettuce (Lactuca sativa) by genome editing and found that it showed an early yellowing phenotype, but only a slight reduction in Chl in presenescent leaves. Thus, this study revealed a conserved but slightly diversified regulation of Chl and LHCP levels via the GLK-BCM pathway in eudicots.