Global gene expression analysis of Aspergillus nidulans reveals metabolic shift and transcription suppression under hypoxia.
Hypoxia imposes a challenge upon most filamentous fungi that require oxygen for proliferation. Here, we used whole genome DNA microarrays to investigate global transcriptional changes in Aspergillus nidulans gene expression after exposure to hypoxia followed by normoxia. Aeration affected the expression of 2,864 genes (27% of the total number of genes in the fungus), of which 50% were either induced or repressed under hypoxic conditions. Up-regulated genes included those for glycolysis, ethanol production, the tricarboxylic acid (TCA) cycle, and for the γ-aminobutyrate (GABA) shunt that bypasses two steps of the TCA cycle. Ethanol and lactate production under hypoxic conditions indicated that glucose was fermented to these compounds via the glycolytic pathway. Since the GABA shunt bypasses the NADH-generating reaction of the TCA cycle catalyzed by oxoglutarate dehydrogenase, hypoxic A. nidulans cells eliminated excess NADH. Hypoxia down-regulated some genes involved in transcription initiation by RNA polymerase II, and lowered the cellular mRNA content. These functions were resumed by re-oxygenation, indicating that A. nidulans controls global transcription to adapt to a hypoxic environment. This study is the first to show that hypoxia elicits systematic transcriptional responses in A. nidulans.
Masuo
Shunsuke
S
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
Terabayashi
Yasunobu
Y
Shimizu
Motoyuki
M
Fujii
Tatsuya
T
Kitazume
Tatsuya
T
Takaya
Naoki
N
D001233:Aspergillus nidulans / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D002952:Citric Acid Cycle; D017931:DNA Primers / Q000235:genetics; D000431:Ethanol / Q000378:metabolism; D015870:Gene Expression; D020869:Gene Expression Profiling; D005800:Genes, Fungal; D018698:Glutamic Acid / Q000378:metabolism; D006019:Glycolysis; D019344:Lactic Acid / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D009243:NAD / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D040081:Protein Array Analysis; D014158:Transcription, Genetic; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D017931:DNA Primers; D009243:NAD; D019344:Lactic Acid; D000431:Ethanol; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D010100:Oxygen