Mutual antagonism between auxin and diacylglycerol acyltransferase 2 regulates high-temperature-induced hypocotyl elongation.

Cell elongation is a fundamental process in plant growth and development, and it is significantly affected by temperature changes. While the signaling mechanisms driving high-temperature-induced cell elongation have been extensively studied, the strategies plants employ to counteract excessive temperature-induced elongation remain poorly understood. Using Arabidopsis thaliana hypocotyls as a model, we show that high temperature induces the triacylglycerol biosynthetic enzyme DGAT2, which acts as a growth-restraining regulator that counterbalances auxin-driven elongation. Auxin, in turn, downregulates DGAT2 expression, establishing a feedback loop that limits excessive hypocotyl elongation under high temperature. Thermo- and auxin-responsive regulation of DGAT2, and its role in modulating membrane lipid order, are conserved between Arabidopsis and Camelina, indicating a shared DGAT2-auxin regulatory module. Our study reveals how lipid metabolism, auxin homeostasis, and membrane dynamics intersect to shape hypocotyl adaptive responses, thereby optimizing growth under high-temperature conditions.