Mutations in the Prokaryotic Pathway Rescue the fatty acid biosynthesis1 Mutant in the Cold  . Issue 1 (29th July 2015)

• Record Type: Journal Article
• Authors: Gao, Jinpeng; Wallis, James G.; Browse, John
• Is Part Of: Plant physiology. Volume 169:Issue 1(2015)
• Page Start: 442
• Page End: 452
• Publication Date: 2015-07-29
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.15.00931
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : Fatty acid biosynthesis mutants are temperature sensitive, but mutations in any of five genes of the prokaryotic lipid synthesis pathway suppress this low-temperature phenotype and rescue cold tolerance. Abstract: The Arabidopsis ( Arabidopsis thaliana ) fatty acid biosynthesis1 ( fab1 ) mutant has increased levels of the saturated fatty acid 16:0 due to decreased activity of 3-ketoacyl-acyl carrier protein (ACP) synthase II. In fab1 leaves, phosphatidylglycerol, the major chloroplast phospholipid, contains up to 45% high-melting-point molecular species (molecules that contain only 16:0, 16:1-trans, and 18:0), a trait associated with chilling-sensitive plants, compared with less than 10% in wild-type Arabidopsis. Although they do not exhibit typical chilling sensitivity, when exposed to low temperatures (2°C–6°C) for long periods, fab1 plants do suffer collapse of photosynthesis, degradation of chloroplasts, and eventually death. A screen for suppressors of this low-temperature phenotype has identified 11 lines, some of which contain additional alterations in leaf-lipid composition relative to fab1 . Here, we report the identification of two suppressor mutations, one in act1, which encodes the chloroplast acyl-ACP:glycerol-3-phosphate acyltransferase, and one in lpat1, which encodes the chloroplast acyl-ACP:lysophosphatidic acid acyltransferase. These enzymes catalyze the first two steps of the prokaryotic pathway for glycerolipid synthesis, so we investigated whether other mutations in this pathway would rescue the fab1 phenotype. Both the gly1 mutation, which reduces glycerol-3-phosphate supply to the prokaryotic pathway, and fad6, which is deficient in the chloroplast 16:1/18:1 fatty acyl desaturase, were discovered to be suppressors. Analyses of leaf-lipid compositions revealed that mutations at all four of the suppressor loci result in reductions in the proportion of high-melting-point molecular species of phosphatidylglycerol relative to fab1 . We conclude that these reductions are likely the basis for the suppressor phenotypes.