title: The catalytic subunit of magnesium-protoporphyrin IX monomethyl ester cyclase forms a chloroplast complex to regulate chlorophyll biosynthesis in rice.
abstract: YGL8 has the dual functions in Chl biosynthesis: one as a catalytic subunit of MgPME cyclase, the other as a core component of FLU-YGL8-LCAA-POR complex in Chl biosynthesis. Magnesium-protoporphyrin IX monomethyl ester (MgPME) cyclase is an essential enzyme involved in chlorophyll (Chl) biosynthesis. However, its roles in regulating Chl biosynthesis are not fully explored. In this study, we isolated a rice mutant yellow-green leaf 8 (ygl8) that exhibited chlorosis phenotype with abnormal chloroplast development in young leaves. As the development of leaves, the chlorotic plants turned green accompanied by restorations in Chl content and chloroplast ultrastructure. Map-based cloning revealed that the ygl8 gene encodes a catalytic subunit of MgPME cyclase. The ygl8 mutation caused a conserved amino acid substitution (Asn182Ser), which was related to the alterations of Chl precursor content. YGL8 was constitutively expressed in various tissues, with more abundance in young leaves and panicles. Furthermore, we showed that expression levels of some nuclear genes associated with Chl biosynthesis were affected in both the ygl8 mutant and YGL8 RNA interference lines. By transient expression in rice protoplasts, we found that N-terminal 40 amino acid residues were enough to localize the YGL8 protein to chloroplast. In vivo experiments demonstrated a physical interaction between YGL8 and a rice chloroplast protein, low chlorophyll accumulation A (OsLCAA). Moreover, bimolecular fluorescence complementation assays revealed that YGL8 also interacted with the other two rice chloroplast proteins, viz. fluorescent (OsFLU1) and NADPH:protochlorophyllide oxidoreductase (OsPORB). These results provide new insights into the roles of YGL8, not only as a subunit with catalytic activity, but as a core component of FLU-YGL8-LCAA-POR complex required for Chl biosynthesis.
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Weiyi
authors: W
authors: Kong
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Xiaowen
authors: X
authors: Yu
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Haiyuan
authors: H
authors: Chen
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Linglong
authors: L
authors: Liu
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Yanjia
authors: Y
authors: Xiao
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Yunlong
authors: Y
authors: Wang
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Chaolong
authors: C
authors: Wang
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Yun
authors: Y
authors: Lin
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Yang
authors: Y
authors: Yu
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Chunming
authors: C
authors: Wang
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Ling
authors: L
authors: Jiang
authors: National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agriculture Sciences, Beijing, 100081, China.
authors: Huqu
authors: H
authors: Zhai
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors: Zhigang
authors: Z
authors: Zhao
authors: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China. wanjm@njau.edu.cn.|National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agriculture Sciences, Beijing, 100081, China. wanjm@njau.edu.cn.
authors: Jianmin
authors: J
authors: Wan
mesh_terms: D020134:Catalytic Domain; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D012275:Oryza / Q000201:enzymology* / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011524:Protoporphyrins / Q000378:metabolism*
chemical_list: D060365:Chloroplast Proteins; D010940:Plant Proteins; D011524:Protoporphyrins; C033434:protoporphyrin IX monomethyl ester
keywords: Chl biosynthesis; FLU-YGL8-LCAA-POR complex; MgPME cyclase; Rice