TY - JOUR T1 - Hello darkness, my old friend: 3-Ketoacyl-Coenzyme A Synthase4 is a branch point in the regulation of triacylglycerol synthesis in Arabidopsis by re-channeling fatty acids under carbon starvation JF - bioRxiv DO - 10.1101/2020.07.27.223388 SP - 2020.07.27.223388 AU - Urszula Luzarowska AU - Anne-Kathrin Ruß AU - Jérôme Joubès AU - Marguerite Batsale AU - Jędrzej Szymański AU - Venkatesh Periyakavanam Thirumalaikumar AU - Marcin Luzarowski AU - Si Wu AU - Feng Zhu AU - Niklas Endres AU - Sarah Khedhayir AU - Julia Schumacher AU - Sandra Marcela Correa Cordoba AU - Aleksandra Skirycz AU - Alisdair Robert Fernie AU - Yonghua Li-Beisson AU - Corina Mariana Fusari AU - Yariv Brotman Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/07/29/2020.07.27.223388.abstract N2 - Due to their sessile lifestyle, plants have evolved unique mechanisms to deal with environmental challenges. Under stress, plant lipids are important as alternative sources of carbon and energy when sugars or starch are limited. Here, we applied combined heat and darkness and extended darkness to a panel of ∼ 300 Arabidopsis accessions to study lipid remodeling under carbon starvation. Natural allelic variation at 3-KETOACYL-COENZYME A SYNTHASE4 (KCS4), a gene encoding for an enzyme involved fatty-acid elongation, underlies a differential accumulation of polyunsaturated triacylglycerols (TAGs) under stress. Ectopic expression in yeast and plants proved that KCS4 is a functional enzyme localized in the ER with specificity for C22 and C24 saturated acyl-CoA. Loss-of-function mutants and transient overexpression in planta revealed the role of KCS4 alleles in TAG synthesis and biomass accumulation. The region harboring KCS4 is under high selective pressure. Furthermore, allelic variation at KCS4 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 light on both plant response mechanisms to abiotic stress and the evolutionary events shaping the lipidome under carbon starvation.One sentence summary Natural variation at KCS4 underlies a differential accumulation of polyunsaturated triacylglycerols, by acting as a regulatory branch point in the fate of fatty acids under carbon starvation. ER -