Over-expression of Arabidopsis ORANGE gene enhances drought stress tolerance through ABA-dependent pathway in Arabidopsis thaliana

Previous studies showed that ORANGE (OR) plays a key role in carotenoid biosynthesis and response to various stress. In this study, we present our discovery of the role of Arabidopsis ORANGE (AtOR) in regulating the ABA-dependent adaptive response to drought stress. For drought tolerance treatment, two weeks old seedlings were transplanted to pots filled with compost soil and subjected to progressive drought treatment for 20 days and re-watered for 2 days. The growth conditions of Arabidopsis were recorded after drought treatment and survival rates were analyzed after re-watering. Quantitative RT-PCR was used to investigate the transcripts levels of AtOR gene under different treatment conditions. Subcellular localization results were obtained by laser scanning confocal microscopy. Overexpression of AtOR significantly enhanced the tolerance to drought stress in Arabidopsis and AtOR was induced by drought and mannitol stresses. Compared with the Col-0 plants, overexpression lines showed slower water loss and smaller stomatal pore size after ABA treatment. Subcellular localization imaging showed that AtOR protein was localized in the chloroplasts. AtOR regulates the expression of ABA- and stress-responsive genes (RAB18, RD29B, RD26, ADH1, ABI2, ABF2) to enhance the tolerance to drought stress.