Overexpression of native ORANGE (OR) and OR mutant protein in Chlamydomonas reinhardtii enhances carotenoid and ABA accumulation and increases resistance to abiotic stress.

The carotenoid content of plants can be increased by overexpression of the regulatory protein ORANGE (OR) or a mutant variant known as the 'golden SNP'. In the present study, a strong light-inducible promoter was used to overexpress either wild type CrOR (CrOR) or a mutated CrOR (CrOR) containing a single histidine substitution for a conserved arginine in the microalgae Chlamydomonas reinhardtii. Overexpression of CrOR and CrOR roughly doubled and tripled, respectively, the accumulation of several different carotenoids, including β-carotene, α-carotene, lutein and violaxanthin in C.