Antisense suppression of violaxanthin de-epoxidase in tobacco does not affect plant performance in controlled growth conditions

Violaxanthin de-epoxidase (VDE) catalyzes the de-epoxidation of violaxanthi n to antheraxanthin and zeaxanthin in the xanthophyll cycle. Tobacco was tr ansformed with an antisense VDE construct under control of the cauliflower mosaic virus 35S promoter to determine the effect of reduced levels of VDE on plant growth. Screening of 40 independent transformants revealed 18 anti sense lines with reduced levels of VDE activity with two in particular (TAS 32 and TAS39) having greater than 95% reduction in VDE activity. Northern a nalysis demonstrated that these transformants had greatly suppressed levels of VDE mRNA. De-epoxidation of violaxanthin was inhibited to such an exten t that no zeaxanthin and only very low levels of antheraxanthin could be de tected after exposure of leaves to high light (2000 mu mol m(-2) s(-1) for 20 min) with no observable effect on levels of other carotenoids and chloro phyll. Non-photochemical quenching was greatly reduced in the antisense VDE tobacco, demonstrating that a significant level of the non-photochemical q uenching in tobacco requires de-epoxidation of violaxanthin. Although the a ntisense plants demonstrated a greatly impaired de-epoxidation of violaxant hin, no effect on plant growth or photosynthetic rate was found when plants were grown at a photon flux density of 500 or 1000 mu mol m(-2) s(-1) unde r controlled growth conditions as compared to wild-type tobacco.