The multistress-induced Translocator protein (TSPO) differentially modulates storage lipids metabolism in seeds and seedlings.
Résumé
Translocator proteins (TSPO) are conserved membrane proteins extensively studied in mammals, but their function is still unclear. Angiosperm TSPO are transiently induced by abiotic stresses in vegetative tissues. We showed previously that constitutive expression of the Arabidopsis TSPO (AtTSPO) could be detrimental to the cell. Degradation of AtTSPO requires an active autophagy pathway. We show here that genetic modifications of TSPO expression in plant and yeast cells reduces the levels of cytoplasmic lipid droplets (LD). Transgenic Arabidopsis seedlings overexpressing AtTSPO contain less LD as compared to wild type. LD levels were increased in Arabidopsis AtTSPO knockout seedlings. Deletion of the Schizosaccharomyces pombe TSPO resulted in an increase of LD level in the cell. As compared to the wild type, the mutant strain was more sensitive to cerulenin, an inhibitor of fatty acids and sterol biosynthesis. We found that in contrast to seedlings, overexpression of AtTSPO (OE) resulted in up to 50% increase in seeds fatty acids as compared to wild type (WT). A time course experiment revealed that after 4 days of seeds imbibition, the levels of triacylglycerol (TAG) was still higher in the OE seeds as compared to WT or knockout (KO) seeds. However, the de novo synthesis of phospholipids and TAG after 24 hours of imbibition was substantially reduced in OE seeds as compared to WT or KO seeds. Our findings support a plant TSPO role in energy homeostasis in a tissue-specific manner, enhancing fatty acids and LD accumulation in mature seeds and limiting LD levels in seedlings. This article is protected by copyright. All rights reserved.