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

Yang Wang#, Ping Zhong#, Xiangyu Zhang, Jiqing Liu, Chaoyang Zhang, Xiaorong Yang, Chunmei Wan, Chuanqiang Liu, Hui Zhou, Bin Yang, Changhui Sun, Xiaojian Deng*, Pingrong Wang*

Plant Science（IF=3.591）,2019，280：321-329

https://www.sciencedirect.com/science/article/pii/S0168945218313463

Abstract

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.