Constitutive BiP protein accumulation in Arabidopsis mutants defective in a gene encoding chloroplast‐resident stearoyl‐acyl carrier protein desaturase. (24th April 2018)

• Record Type: Journal Article
• Authors: Iwata, Yuji; Iida, Tsukasa; Matsunami, Toshihiro; Yamada, Yu; Mishiba, Kei‐ichiro; Ogawa, Takumi; Kurata, Tetsuya; Koizumi, Nozomu
• Is Part Of: Genes to cells. Volume 23:Number 6(2018)
• Page Start: 456
• Page End: 465
• Publication Date: 2018-04-24
• Subjects: Arabidopsis thaliana -- binding protein -- endoplasmic reticulum stress -- fatty acid -- stearoyl‐acyl carrier protein desaturase -- unfolded protein response; Cytogenetics -- Periodicals; Cells -- Mechanical properties -- Periodicals; Molecular genetics -- Periodicals; Genes -- Periodicals; Molecular biology -- Periodicals; Cytology -- Periodicals; Biomechanics -- Periodicals; 571.6
• DOI: 10.1111/gtc.12585
• Languages: English
• ISSNs: 1356-9597

Abstract

Abstract : The unfolded protein response (UPR) occurs when protein folding and maturation are disturbed in the endoplasmic reticulum (ER). During the UPR, a number of genes including those encoding ER‐resident molecular chaperones are induced. In Arabidopsis, BiP3 has been used as a UPR marker gene whose expression is strongly induced in response to ER stress. In this study, we mutagenized Arabidopsis plants expressing β ‐glucuronidase ( GUS ) gene under the control of BiP3 promoter and isolated a mutant that exhibits strong GUS activity without treatment with ER stress inducers. By whole genome sequencing, we identified a causal gene in the mutant as SUPPRESSOR OF SALICYLIC ACID INSENSITIVITY2 ( SSI2 ), which encodes stearoyl‐acyl carrier protein desaturase that converts stearic acids to oleic acids in the chloroplasts. In addition to GUS proteins, the ssi2 mutant accumulates endogenous BiP3 proteins without treatment by any stress reagents. Interestingly, although the degree of endogenous BiP3 protein accumulation in the ssi2 mutant was comparable to that in wild‐type plants treated with the ER stress inducer tunicamycin, much less BiP3 transcripts were detected in the ssi2 mutant compared to tunicamycin‐treated wild‐type plants. Our finding suggests a genetic link between fatty acid metabolism in the chloroplasts and ER functions. Abstract : This study reports identification and characterization of an Arabidopsis mutant that constitutively accumulates the ER chaperone BiP3 without ER stress inducers. The causal gene encodes stearoyl‐acyl carrier protein desaturase in the chloroplasts, suggesting a genetic link between fatty acid metabolism in the chloroplasts and ER functions.