Overexpression of AtchyB in Eustoma grandiflorum Shinn Enhances its Tolerance to High-Light Via Zeaxanthin Accumulation.

Carotenoids are essential components of the photosynthetic apparatus involved in plant photoprotection. To investigate the protective role of zeaxanthin and the xanthophyll cycle under high-light stress, we increased the capacity for their biosynthesis in Eustoma grandiflorum Shinn by overexpression of a gene ( AtchyB) from Arabidopsis thaliana encoding β-carotene hydroxylase (BCH). This enzyme is involved in the conversion of β-carotene into zeaxanthin and plays an important role in the carotenoid biosynthetic pathway. Not only was the total carotenoid content of the transgenics enhanced (1.046- to 3.141-fold) but zeaxanthin biosynthesis was also faster and the compound was produced in larger quantities in transgenics (up to 3.344-fold) than in controls upon exposure to high-light stress. Additionally, a greater amount of xanthophyll cycle pigments (1.46- to 2.44-fold) was detected in the transgenics. Under high-light stress, untransformed controls showed obvious growth retardation, while transformants were more tolerant. The net addition of biomass in the transformants was more than that of non-transformants under high-light exposure. Furthermore, a new phenomenon was found: high-light stress induced an apparent periodical accumulation of biomass and zeaxanthin in transformants. Our results supplement data from previous research, and indicate that the periodic enhancement of zeaxanthin formation together with the periodic enlargement of the xanthophyll cycle pool contributes to long-term high-light stress protection and prevents plant damage. [ABSTRACT FROM AUTHOR]