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

During droughting plants activate a number of genes involved in adaptation to water stress. We have isolated one such gene, btg-26, from Brassica 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 already increased six-fold over levels found in leaf tissue from fully hydrated 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 temperature, heat shock and the plant hormone abscisic acid. Analysis of the deduced amino acid sequence revealed similarity to the dehydrogenase family of enzymes. These results suggest that btg-26 encodes a protein whose function may be required early during general osmotic stress in some unknown adaptive metabolic pathway.