title: Transgenic tobacco with suppressed zeaxanthin formation is susceptible to stress-induced photoinhibition.
abstract: Tobacco (Nicotiana tabacum cv. Xanthi) transformed with the antisense construct of tobacco violaxanthin de-epoxidase was analyzed for responses in growth chambers to both short and long-term stress treatments. Following a short-term (2 or 3 h) high-light treatment, antisense plants had a greater reduction in F(v)/F(m) relative to wild-type, indicating a greater susceptibility to photoinhibition. The responses of antisense plants to long-term stress were examined in two separate experiments, one with high light alone and the other wherein high light and water stress were combined. In the light-stress experiment, plants were grown at 1300 mumol photons m(-2) s(-1) under a 12 h photoperiod. In the light and water-stress experiment, plants were grown under moderately high light of 900 mumol photons m(-2) s(-1), under a 16 h photoperiod, in combination with water stress. Both conditions caused formation of high antheraxanthin and zeaxanthin levels in wild-type plants but not in antisense plants. In both cases, antisense plants showed significant reductions in F(v)/F(m) and total leaf-pigment content relative to wild-type. The data demonstrate a critical photoprotective function of the xanthophyll cycle-dependent energy dissipation in tobacco exposed suddenly to high amounts of excess light over extended times.
authors.affiliation: Department of Biology, University of St. Thomas, 2115 Summit Avenue, St. Paul, MN, 55105-1096, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Verhoeven
authors.forename: R C
authors.initials: RC
authors.lastname: Bugos
authors.forename: H Y
authors.initials: HY
authors.lastname: Yamamoto