GUN4 Is Required for Posttranslational Control of Plant Tetrapyrrole Biosynthesis

作     者：Enrico Peter Bernhard Grimm 

作者机构：Institute of Biology/Plant Physiology Humboldt University Philippstr. 13 Building 12 D 10115 Berlin Germany 

出 版 物：《Molecular Plant》 (分子植物（英文版）)

年 卷 期：2009年第2卷第6期

页      面：1198-1210页

核心收录：

学科分类：0710[理学-生物学] 1007[医学-药学(可授医学、理学学位)] 100705[医学-微生物与生化药学] 0828[工学-农业工程] 08[工学] 0901[农学-作物学] 0902[农学-园艺学] 10[医学] 

基　　金：The authors acknowledge funding by DFG Studienstiftung des deutschen Volkes to E.P. No conflict of interest declared 

主　　题：Tetrapyrrole biosynthesis chlorophyll Mg porphyrin branch photo-oxidation chloroplasts 

摘      要：In aerobic photosynthetic organisms, GUN4 binds the chlorophyll intermediates protoporphyrin and Mg protoporphyrin, stimulates Mg chelatase activity, and is implicated in plastidic retrograde signaling. GUN4 expression is most abundant in young and greening tissues and parallels the activity of 5-aminolevulinic acid （ALA） ALA and Mg porphyrin biosynthesis during photoperiodic growth. We explored function and mode of action of GUN4 using GUN4- deficient and overexpressing plants. GUN4 overexpression leads to a general activation of the enzymes of chlorophyll biosynthesis. During photoperiodic growth GUN4 deficiency prevents ALA synthesis and chlorophyll accumulation. All these metabolic changes do not correlate with altered gene expression or changes of protein abundance in tetrapyrrole biosynthesis. While ALA feeding fails to compensate GUN4 deficiency during light-dark growth, this approach results in chlorophyll accumulation under continuous dim light. A new model defines the involvement of GUN4 in posttranslational regulation of ALA and Mg porphyrin synthesis, to sustain chlorophyll synthesis, namely under varying environmental conditions.