MOLECULAR-CLONING AND EXPRESSION OF A TURGOR-RESPONSIVE GENE IN BRASSICA-NAPUS

During droughting plants activate a number of genes involved in adapta tion to water stress. We have isolated one such gene, btg-26, from Bra ssica napus. Expression of btg-26 is induced in leaf tissue within 72 h of withholding water. At 81% relative water content (RWC), when the plant is just beginning to show signs of wilting, expression is alread y increased six-fold over levels found in leaf tissue from fully hydra ted plants. btg-26 expression reaches a maximum eleven-fold induction at 63% RWC, then transcript levels decrease as RWC continues to drop. btg-26 is also activated in plants exposed to high salinity, low tempe rature, heat shock and the plant hormone abscisic acid. Analysis of th e deduced amino acid sequence revealed similarity to the dehydrogenase family of enzymes. These results suggest that btg-26 encodes a protei n whose function may be required early during general osmotic stress i n some unknown adaptive metabolic pathway.