Glycerol dehydrogenase, encoded by gldB is essential for osmotolerance in Aspergillus nidulans.
We have characterized the Aspergillus nidulans gldB gene encoding a NADP+-dependent glycerol dehydrogenase. A basal expression level was observed for gldB, which increased significantly under conditions of hyper-osmotic shock (1 M NaCl). Growth of strains in which gldB was disrupted was severely reduced on plates containing 1% glucose and 1 M NaCl, but these strains were able to grow on plates containing 1 M NaCl and 1% glycerol, arabitol, mannitol or erythritol. Uptake of these polyols compensated for the inability of the gldB disruptants to produce glycerol. Presence of 1% glucose in these plates prevented growth restoration by all the polyols tested with the exemption of glycerol, indicating that uptake of mannitol, arabitol and erythritol is subject to glucose repression, whereas uptake of glycerol is significantly less or not repressed. No intracellular glycerol dehydrogenase activity could be detected in the gldB disruption strains. Intracellular glycerol levels in these strains were strongly decreased compared to wild type, whereas intracellular mannitol, erythritol and arabitol levels were increased. Conidia of the gldB disruption strain did not accumulate glycerol upon germination in glucose media with or without 1 M NaCl and germ tube emergence was significantly delayed in this strain in the presence of 1 M NaCl in comparison to the wild type. These data indicate that gldB is essential for osmotolerance in A. nidulans and that the pathways for glycerol biosynthesis under osmotic stress differ between yeast and filamentous fungi.
de Vries
Ronald P
RP
Molecular Genetics of Industrial Microorganisms, Wageningen University, Dreijenlaan 2, 6703 HA Wageningen, The Netherlands. r.p.devries@bio.uu.nl
Flitter
Simon J
SJ
van de Vondervoort
Peter J I
PJ
Chaveroche
Marie-Kim
MK
Fontaine
Thierry
T
Fillinger
Sabine
S
Ruijter
George J G
GJ
d'Enfert
Christophe
C
Visser
Jaap
J
D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D002455:Cell Division; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D020868:Gene Silencing; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D008969:Molecular Sequence Data; D009249:NADP / Q000378:metabolism; D009994:Osmolar Concentration; D012965:Sodium Chloride / Q000378:metabolism; D013401:Sugar Alcohol Dehydrogenases / Q000235:genetics* / Q000378:metabolism*; D013402:Sugar Alcohols / Q000378:metabolism
D005656:Fungal Proteins; D013402:Sugar Alcohols; D012965:Sodium Chloride; D009249:NADP; D013401:Sugar Alcohol Dehydrogenases; C020672:glycerol dehydrogenase; D005947:Glucose; D005990:Glycerol