Biosynthetic pathways of glycerol accumulation under salt stress in Aspergillus nidulans.
A culture of Aspergillus nidulans (FGSC 359) was gradually adapted for growth in media containing up to 2 M NaCl or was exposed to a salt shock with 2 M NaCl. The intracellular glycerol level increased by about 7.9-fold in salt-adapted and 2.4-fold in salt-shocked cultures when compared to the unadapted culture. The biosynthetic pathway involved in the accumulation of glycerol was investigated under long-term salt adaptation and short-term salt shock. Glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) was induced 1.4-fold in salt-shocked but not in salt-adapted cultures. An alternate enzymatic pathway involving glycerol dehydrogenase (NADP(+)-dependent) utilizing dihydroxyacetone (DHA) and/or DL-glyceraldehyde (DL-GAD) was induced by NaCl. DHA-dependent glycerol dehydrogenase activity was induced about 6.3-fold in salt-adapted and 1.35-fold in salt-shocked cultures, while DL-GAD-dependent activity was induced about 6.1-fold in salt-adapted and 1.2-fold in salt-shocked cultures. However, the level of glycerol dehydrogenase activity with DL-GAD as substrate was 7% of the DHA-dependent activity. We conclude that a salt-inducible NADP(+)-dependent glycerol dehydrogenase activity electrophoretically indistinguishable from previously described glycerol dehydrogenase I results in glycerol accumulation in salt-stressed A. nidulans.
Redkar
R J
RJ
Department of Botany and Microbiology, Auburn University, Alabama 36849-5407, USA.
Locy
R D
RD
Singh
N K
NK
D001233:Aspergillus nidulans / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D005990:Glycerol / Q000378:metabolism*; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D013401:Sugar Alcohol Dehydrogenases / Q000378:metabolism
D012462:Saline Solution, Hypertonic; D009243:NAD; D009249:NADP; D005993:Glycerolphosphate Dehydrogenase; D013401:Sugar Alcohol Dehydrogenases; C020672:glycerol dehydrogenase; D005990:Glycerol