Plant stress caused by increased sunlight is an important component in crop yield reduction, but the biochemical mechanisms that lead to this problem have been unclear. In 11 July Nature, P Davison and colleagues at the University of Sheffield, UK, show that overexpression of β-carotene hydroxylase can enhance stress tolerance in Arabidopsis thaliana and may protect plants against increased sunlight and temperature (Nature 2002, 418:203-206).

The xanthophyll cycle is a reversible interconversion of two carotenoids, violaxanthin and zeaxanthin and has a key photoprotective role. Davison et al. observed that in A. thaliana overexpression of the chyB gene (which encodes β-carotene hydroxylase) causes a specific twofold increase in the size of the xanthophyll cycle pool. The genetically modified plants were more tolerant to conditions of high light and high temperature, showing reduced leaf necrosis, reduced production of the stress indicator anthocyanin and reduced lipid peroxidation.


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