title: The Glycosyltransferase QUA1 Regulates Chloroplast-Associated Calcium Signaling During Salt and Drought Stress in Arabidopsis.
abstract: Cytoplasmic Ca2+ ([Ca2+]cyt) elevation induced by various signals is responsible for appropriate downstream responses. Through a genetic screen of Arabidopsis thaliana mutants defective in stress-induced [Ca2+]cyt elevation, the glycosyltransferase QUASIMODO1 (QUA1) was identified as a regulator of [Ca2+]cyt in response to salt stress. Compared with the wild type, the qua1-4 mutant exhibited a dramatically greater increase in [Ca2+]cyt under NaCl treatment. Functional analysis showed that QUA1 is a novel chloroplast protein that regulates cytoplasmic Ca2+ signaling. QUA1 was detected in chloroplast thylakoids, and the qua1-4 mutant exhibited irregularly stacked grana. The observed greater increase in [Ca2+]cyt was inhibited upon recovery of chloroplast function in the qua1-4 mutant. Further analysis showed that CAS, a thylakoid-localized calcium sensor, also displayed irregularly stacked grana, and the chloroplasts of the qua1-4 cas-1 double mutant were similar to those of cas-1 plants. In QUA1-overexpressing plants, the protein level of CAS was decreased, and CAS was readily degraded under osmotic stress. When CAS was silenced in the qua1-4 mutant, the large [Ca2+]cyt increase was blocked, and the higher expression of PLC3 and PLC4 was suppressed. Under osmotic stress, the qua1-4 mutant showed an even greater elevation in [Ca2+]cyt and was hypersensitive to drought stress. However, this sensitivity was inhibited when the increase in [Ca2+]cyt was repressed in the qua1-4 mutant. Collectively, our data indicate that QUA1 may function in chloroplast-dependent calcium signaling under salt and drought stresses. Additionally, CAS may function downstream of QUA1 to mediate these processes.
authors.affiliation: School of Agricultural Engineering, Nanyang Normal University, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, China.
authors.forename: Chancan
authors.initials: C
authors.lastname: Liao
authors.affiliation: Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, China.
authors.forename: Shuangshuang
authors.initials: S
authors.lastname: Zhao
authors.affiliation: PLA army general hospital, China.
authors.forename: Chongwu
authors.initials: C
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Guo
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics; D002736:Chloroplasts / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000235:genetics; D006602:Hexosyltransferases / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; D012965:Sodium Chloride; D006602:Hexosyltransferases; C508259:QUA1 protein, Arabidopsis; D002118:Calcium
keywords: CAS; Calcium signaling; Chloroplast; Drought stress; QUA1; Salt stress