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.