Specific expression of glucose-6-phosphate dehydrogenase (G6PDH) gene by salt stress in wheat (Triticum aestivum L.)

We isolated three kinds of full-length cDNA clones for glucose-6-phosphate dehydrogenase (G6PDH) from wheat. They showed over 80% sequence homology with potato and alfalfa at the amino acid level, suggesting that the genes are highly conserved in angiosperms. The lack of a plastidic signal sequence, as well as a higher transcript accumulation level in roots than leaves, suggested that the wheat cDNA sequences encode the cytosolic isoform of the enzyme. Genomic Southern analysis revealed that the isoform is encoded by a few copies of the gene in the wheat genome. Southern analysis of nullisomic-tetrasomic lines suggested that at least one gene is located on chromosome 2B. The G6PDH transcript started to accumulate in the roots after 2 h of 0.15 M NaCl treatment, reaching its maximal level after 12 h of exposure. The G6PDH gene did not respond to either mannitol or abscisic acid (ABA) treatment. The NaCl-specific early response of the G6PDH gene is discussed in relation to the putative role of the enzyme in the salt stress response in plants.