Regulation of lipid synthesis in Arabidopsis thaliana under diverse abiotic stress conditions

LUZAROWSKA U; RUSS A-K; FUSARI CM; BROTMAN Y

Potsdam

Simposio; Plant Stress Symposium 2018 on Oxidative and Abiotic Stress; 2018

Universidad Potsdam

We conducted two-environment genome-wide association studies (GWAS), using lipid levels as quantitative traits, with a panel of 314 Arabidopsis thaliana accessions grown in control condition and combined stress of heat and darkness. This resulted in high number of lipid quantitative trait loci (QTLs), many of which are condition specific. Recognition of approximately 200 environmental specific QTLs indicates genome plasticity for the regulation of lipid biosynthesis under abiotic stress. The 3-ketoacyl-CoA synthase 4 (KCS4) gene, a heretofore-uncharacterized KCS, emerged as a prominent gene of lipid regulation, with dozens of highly polyunsaturated triacylglycerols (TAGs) mapping to it with CXremarkable statistical robustness (p-value < 10?15). Very long chain fatty acids (VLCFA), with 20-carbon chains or longer, are synthesized by incremental elongation of the chain, mediated by elongase enzymes. KCS4, with 21 members in Arabidopsis, is the first enzyme of the elongase complex and is also the rate-limiting and specificity-determining component of the complex. Many of the twenty-one KCS genes in Arabidopsis have been studied, but KCS4 specificity and function remain unknown. Polyunsaturated fatty acids are known to release from the membrane upon stress, and to cause oxidative damage to cell components. Often, however, cell mechanisms manage to sequester these fatty acids in TAGs, thereby exerting protection against this so-called lipotoxicity. The effect of KCS4 on the sequestration of polyunsaturated fatty acids into TAGs under abiotic stress indicates that KCS4 stands at a major junction in lipid metabolism, and the extreme variation in the natural abundance of the KCS4 may provide insights about plant response mechanisms to abiotic stress and to the adaptive selection pressures that shape them.