PARENT SESSION
Posters P1B Photo-oxidative stress, photoinhibition. Abstracts (394-443)

Characterisation of Arabidopsis plants overexpressing -carotene hydroxylase. Matt Johnson^*,1, Paul Davison, Erik Murchie, Mark Wentworth, Peter Horton, ¹ Department of Molecular Biology & Biotechnology, Sheffield, United Kingdom

ABSTRACT- In higher plants, high light stress leads to the production of reactive oxygen species that cause damage to the photosynthetic thylakoid membrane. We have successfully transformed Arabidopsis with a construct containing the chyB gene encoding the carotenoid biosynthetic pathway enzyme -carotene hydroxylase. Carotenoids in the thylakoid membrane help to protect the photosynthetic apparatus from photo-oxidative stress. In plants, the xanthophyll cycle (the reversible interconversion of the carotenoids violaxanthin and zeaxanthin) has a key photoprotective role. The overexpression of this enzyme causes a two-fold increase in the amount of xanthophyll cycle carotenoids. We have previously described that the transformed lines show enhanced high light and high temperature stress tolerance. Recent work has focused on the molecular and physiological characterisation of these plants. The transformed plants show more rapid production of zeaxanthin upon illumination and longer retention in the dark compared to wild type, as shown by change in absorbance at 505nm. The transformed plants also show slower relaxation of non-photochemical quenching, as shown by chlorophyll fluorescence. No perturbation of the rest of the carotenoid biosynthetic pathway has been observed nor has any difference in leaf abscisic acid content. The photosynthetic characteristics of these plants will also be presented.

KEY WORDS: abiotic stress, xanthophyll cycle, zeaxanthin, non-photochemical quenching