Ectopic expression of the Lycium barbarum β-carotene hydroxylase gene (chyb) enhances drought and salt stress resistance by increasing xanthophyll cycle pool in tobacco

Abstract

Abiotic stresses, such as drought and salinity, are major limiting factors for plant growth and reproduction. Carotenoids play key roles in response to abiotic stresses. To identify the role of Lycium barbarum β-carotene hydroxylase gene (chyb) under drought and salt stress, we checked the physiological and biochemical properties of chyb-overexpressing transgenic tobacco. Ectopic expression of chyb in tobacco increased the drought and salt tolerance in the transgenic lines. The amounts of xanthophylls cycle pigments were significantly increased in the transgenic lines compared with the controls. Under osmotic stress conditions, the root length and shoot biomass of the transgenic lines were significantly increased. Under drought stress conditions, the transgenic lines leaves lost water slower than the WT plants and the photosynthesis rate and SOD activity were significantly increased, whereas stomatal conductance and malondialdehyde content were decreased in the transgenic lines. Under salt stress conditions, proline and chlorophyll levels of the transgenic lines were significantly increased, whereas malondialdehyde and Na+/K+ ratios were significantly decreased. Thus, these findings suggest that L. barbarum chyb gene dramatically enlarge the xanthophyll cycle pool size, which plays an important role in resistance to drought and salt stress in tobacco.