Overexpression of β-carotene hydroxylase enhances stress tolerance in Arabidopsis

Plant stress caused by extreme environmental conditions is already a principal reason for yield reduction in crops1. The threat of global environment change makes it increasingly important to generate crop plants that will withstand such conditions. Stress, particularly stress caused by increased sunlight, leads to the production of reactive oxygen species that cause photo-oxidative cell damage2. Carotenoids, which are present in the membranes of all photosynthetic organisms, help protect against such light-dependent oxidative damage3. In plants, the xanthophyll cycle (the reversible interconversion of two carotenoids, violaxanthin and zeaxanthin4) has a key photoprotective role5 and is therefore a promising target for genetic engineering to enhance stress tolerance. Here we show that in Arabidopsis thaliana overexpression of the chyB gene that encodes β-carotene hydroxylase—an enzyme in the zeaxanthin biosynthetic pathway6—causes a specific twofold increase in the size of the xanthophyll cycle pool. The plants are more tolerant to conditions of high light and high temperature, as shown by reduced leaf necrosis, reduced production of the stress indicator anthocyanin and reduced lipid peroxidation. Stress protection is probably due to the function of zeaxanthin in preventing oxidative damage of membranes.