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Hormonal and environmental regulation of the carrot lea-class gene Dc3

Vivekananda, J., Drew, M.C., Thomas, T.L.
Plant physiology 1992 v.100 no.2 pp. 576-581
Daucus carota, Nicotiana tabacum, multigene family, recombinant DNA, reporter genes, beta-glucuronidase, gene expression, abscisic acid, water stress, messenger RNA, genetic transformation, transgenic plants, leaf water potential, promoter regions, histochemistry
Dc3 is a carrot lea-class gene belonging to a small gene family that encodes Dc3 and Dc3-like RNA sequences. We have examined the responsiveness to water deficit and abscisic acid (ABA) of the promoter/enhancer complex of Dc3 fused to a beta-glucuronidase (GUS) reporter gene in vegetative cells of transgenic tobacco. In 56-d tobacco, GUS expression in leaves increased about 200-fold during a 3-d drying cycle, during which there were small decreases (3 atmospheres or less) in leaf water potential and a 16-fold increase in free ABA. These effects were reversed by rewatering. Changes in GUS activity were closely paralleled by changes in GUS transcript levels during the desiccation/watering cycle, indicating transcriptional regulation of GUS gene expression. The Dc3 promoter responds to exogenous ABA; the effect is time and concentration dependent, with greater than 10-fold induction in 8 h with 10 microgram ABA. Histochemical visualization of GUS activity in seedlings induced by water deficit or exogenous ABA revealed Dc3-driven GUS expression in all organs of transgenic tobacco seedlings. We suggest that the DC3/GUS reporter system is a sensitive analytical tool to study various environmental effects on plant growth and development.