title: A knockdown mutation of YELLOW-GREEN LEAF2 blocks chlorophyll biosynthesis in rice.
abstract: An insert mutation of YELLOW-GREEN LEAF2 , encoding Heme Oxygenase 1 , results in significant reduction of its transcript levels, and therefore impairs chlorophyll biosynthesis in rice. Heme oxygenase (HO) in higher plants catalyzes the degradation of heme to synthesize phytochrome precursor and its roles conferring the photoperiodic control of flowering in rice have been revealed. However, its involvement in regulating rice chlorophyll (Chl) synthesis is not fully explored. In this study, we isolated a rice mutant named yellow-green leaf 2 (ygl2) from a (60)Co-irradiated population. Normal grown ygl2 seedlings showed yellow-green leaves with reduced contents of Chl and tetrapyrrole intermediates whereas an increase of Chl a/b ratio. Ultrastructural analyses demonstrated grana were poorly stacked in ygl2 mutant, resulting in underdevelopment of chloroplasts. The ygl2 locus was mapped to chromosome 6 and isolated via map-based cloning. Sequence analysis indicated that it encodes the rice HO1 and its identity was verified by transgenic complementation test and RNA interference. A 7-Kb insertion was found in the first exon of YGL2/HO1, resulting in significant reduction of YGL2 expressions in the ygl2 mutant. YGL2 was constitutively expressed in a variety of rice tissues with the highest levels in leaves and regulated by temperature. In addition, we found expression levels of some genes associated with Chl biosynthesis and photosynthesis were concurrently altered in ygl2 mutant. These results provide direct evidence that YGL2 has a vital function in rice Chl biosynthesis.
authors.affiliation: National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Cheng
authors.forename: Xiaoding
authors.initials: X
authors.lastname: Ma
authors.forename: Han
authors.initials: H
authors.lastname: Wu
authors.forename: Yanling
authors.initials: Y
authors.lastname: Liu
authors.forename: Kunneng
authors.initials: K
authors.lastname: Zhou
authors.forename: Yilin
authors.initials: Y
authors.lastname: Chen
authors.forename: Weiwei
authors.initials: W
authors.lastname: Ma
authors.forename: Jingcui
authors.initials: J
authors.lastname: Bi
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Xiuping
authors.initials: X
authors.lastname: Guo
authors.forename: Jiulin
authors.initials: J
authors.lastname: Wang
authors.forename: Cailin
authors.initials: C
authors.lastname: Lei
authors.forename: Fuqing
authors.initials: F
authors.lastname: Wu
authors.forename: Qibing
authors.initials: Q
authors.lastname: Lin
authors.forename: Yuqiang
authors.initials: Y
authors.lastname: Liu
authors.forename: Linglong
authors.initials: L
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002734:Chlorophyll / Q000096:biosynthesis*; D032461:Chromosomes, Plant / Q000235:genetics; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D017343:Genes, Plant / Q000235:genetics; D005816:Genetic Complementation Test; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D058503:Mesophyll Cells / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D012275:Oryza / Q000201:enzymology / Q000235:genetics*; D010788:Photosynthesis / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013696:Temperature; D020524:Thylakoids / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D002734:Chlorophyll; D006419:Heme Oxygenase (Decyclizing)
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