3-Ketoacyl-Coenzyme A Synthase4 regulates triacylglycerol synthesis in Arabidopsis thaliana under combined heat and dark stress

LUZAROWSKA U; RUSS A-K; SZYMANSKI J; JOUBÈS J; THIRUMALAI KUMAR V. P; FERNIE A. R.; FUSARI CM; BROTMAN Y

Congreso; Plant Biology 2020 Worldwide Summit; 2020

American Society of Plant Biologist

Due to their sessile lifestyle, plants have evolved unique mechanisms to deal with multiple environmental challenges. Under stress, plant lipids are important as an alternative source of carbon and energy when sugars or starch are limited. We applied combined heat and darkness and extended darkness to a panel of ~ 300 Arabidopsis natural accessions and performed Genome-Wide Association Studies (GWAS) to study the genetic regulation of lipid remodeling under carbon starvation. We identified that natural allelic variation in 3-KETOACYL-COENZYME A SYNTHASE4 (KCS4), a gene encoding for an enzyme involved in the elongation of very long chain fatty acids, underlies a differential accumulation of polyunsaturated triacylglycerols (TAGs) under stress. Using ectopic expression in yeast and plants we demonstrated that KCS4 is a functional enzyme localized in the ER with specificity for C22 and C24 saturated acyl-CoA. Loss-of-function Arabidopsis mutants and transient overexpression in leaves of Nicotiana benthamiana allowed us to explore the role of the different alleles at KCS4 in TAG synthesis and biomass accumulation under different growth conditions. We identified that the region harboring KCS4 is under high selective pressure. Furthermore, the allelic variation at KCS4 was correlated with environmental parameters from the locales of Arabidopsis accessions. Our results provide evidence that KCS4 plays a decisive role in the subsequent fate of fatty acids released from chloroplast-membrane lipids under carbon starvation. This work sheds new light on both plant response mechanisms to abiotic stress and the evolutionary events that shape the lipidome under carbon starvation.