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GRA78 encoding a putative S-sulfocysteine synthase is involved in chloroplast development at the early seedling stage of rice

Wang, Yang, Zhong, Ping, Zhang, Xiangyu, Liu, Jiqing, Zhang, Chaoyang, Yang, Xiaorong, Wan, Chunmei, Liu, Chuanqiang, Zhou, Hui, Yang, Bin, Sun, Changhui, Deng, Xiaojian, Wang, Pingrong
Plant science 2019 v.280 pp. 321-329
Arabidopsis, Oryza sativa, albino, catalytic activity, chloroplasts, cysteine, cysteine synthase, gene expression, gene expression regulation, genes, leaves, molecular cloning, mutants, mutation, phenotypic plasticity, photoperiod, photosynthesis, proteins, quantitative polymerase chain reaction, reverse transcriptase polymerase chain reaction, rice, seedlings, temperature, thiols, tissues
Cysteine functions not only as an amino acid in proteins but also as a precursor for a large number of essential biomolecules. Cysteine is synthesized via the incorporation of sulfide to O-acetylserine under the catalysis of O-acetylserine(thiol)lyase (OASTL). In dicotyledonous Arabidopsis, nine OASTL genes have been reported. However, in their null mutants, only the mutant of CS26 encoding S-sulfocysteine synthase showed the visible phenotypic changes, displaying significantly small plants and pale-green leaves under long-day condition but not short-day condition. Up to now, no OASTL gene or mutant has been identified in monocotyledon. In this study, we isolated a green-revertible albino mutant gra78 in rice (Oryza sativa). Its albino phenotype at the early seedling stage was sensitive to temperature but independent of photoperiod. Map-based cloning revealed that candidate gene LOC_Os01g59920 of GRA78 encodes a putative S-sulfocysteine synthase showing significant similarity with Arabidopsis CS26. Complementation experiment confirmed that mutation in LOC_Os01g59920 accounted for the mutant phenotype of gra78. GRA78 is constitutively expressed in all tissues and its encoded protein is targeted to the chloroplast. In addition, qRT-PCR suggested that expression levels of four OASTL homolog genes and five photosynthetic genes were remarkably down-regulated.