| Carbohydrates are proposed to stabilize membranes, protect proteins, and contribute to cellular osmoregulation during drought stress. Microarray technology was utilized to study changes in the steady-state level of transcripts encoding enzymes involved in carbon metabolism (i.e. photosynthesis, carbohydrate and inositol phosphate metabolism) and glycerolipid metabolism under drought-stress.; Microarray-based expression data of 49 genes included in our study were integrated into the Kyoto Encyclopedia of Genes and Genomes (KEGG) carbon metabolism (i.e. photosynthesis: thylakoid electron transport pathway and carbon fixation, glycolysis, starch and sucrose metabolism, and the inositol phosphate pathway) and glycerolipid pathway database. Our results indicated that photosynthetic genes were suppressed, whereas, glycolytic genes were primarily induced under drought. Concomitantly, we found that glucose levels decreased three-fold in the drought treatment, when compared to the control treatment. These results suggest that during drought, alfalfa leaf carbohydrates (i.e. glucose) may be metabolized in the glycolytic pathway, possibly to generate ATP and NADPH (reducing energy), in the absence of photosynthesis.; Enzyme genes involved in starch degradation and sucrose metabolism, were primarily induced under drought. These results indicate that starch may be degraded to provide carbon skeletons for basic metabolic processes including energy production via glycolysis. Sucrose may be synthesized for export to alfalfa roots and crowns to support regrowth if the shoot dies.; Enzyme genes involved in the synthesis of osmoprotectants (i.e. myo-inositol and D-pinitol) via glucose conversion were primarily induced under drought. Concomitantly, D-pinitol levels increased two-fold in the drought treatment, when compared to the control treatment, suggesting that D-pinitol accumulates during drought-stress in alfalfa leaves. (Abstract shortened by UMI.)... |
