Transcriptional analysis of genes for energy catabolism and hydrolytic enzymes in the filamentous fungus Aspergillus oryzae using cDNA microarrays and expressed sequence tags

Abstract

Aspergillus oryzae is a fungus used extensively in the fermentation industry. We constructed cDNA microarrays comprising 2,070 highly expressed cDNAs selected from the approximately 6,000 non-redundant expressed sequence tags (ESTs) in the A. oryzae EST database (http://www.aist.go.jp/RIODB/ffdb/index.html). Using the cDNA microarrays, we analyzed the gene expression profiles of A. oryzae cells grown under the glucose-rich (AC) and glucose-depleted (AN) liquid culture conditions used during the construction of the EST database. The sets of genes identified by the cDNA microarray as highly expressed under each culture condition agreed well with the highly redundant ESTs obtained under the same conditions. In particular, transcription levels of most catabolic genes of the glycolytic pathway (EMP) and tricarboxylic acid (TCA) cycle were higher under AC than AN conditions, suggesting that A. oryzae uses both EMP and TCA for glucose metabolism under AC conditions. We further studied the expression of genes encoding hydrolytic enzymes and enzymes involved in energy catabolism by using three industrial solid-phase biomass media, including wheat-bran. The wheat-bran culture gave the richest gene expression profile of hydrolytic enzymes and the lowest expression levels of catabolic genes (EMP, TCA) among the three media tested. The low expression levels of catabolic genes in the wheat-bran culture may release catabolite repression, consequently leading to the rich expression profiles of the hydrolytic enzymes.

Genome sequencing and analysis of Aspergillus oryzae

“…It has been reported that yeast chromosomes are rearranged frequently under starved culture conditions and that (AþT)-rich sequences or transfer RNA often mediate such rearrangements 20 . Our EST analysis shows that the expression profile in solid-state cultivation is similar to that observed when a carbon source is omitted 21 . These reports suggest that the acquired foreign DNA has been rearranged in a short period of time by large-scale solid-state cultivation since A. oryzae was domesticated from an ancestor of A. flavus 22 .…”

The β-1,3-Exoglucanase GeneexgA(exg1) ofAspergillus oryzaeIs Required to Catabolize Extracellular Glucan, and Is Induced in Growth on a Solid Surface

“…While exgA expression showed significant differences in some of the culture conditions described above, expression of the histone H4 gene, which showed expression typical of a housekeeping gene as control, 28) remained constant in all the culture conditions used in this study (Fig. 4E).…”

“…28,31) Limitation of nutrition in solid state culture leads to the production of more hydrolases than in nutrition-rich conditions. 28) Riou et al have reported that ExgA productivity was highest when A. oryzae was grown with a carbon source of water-insoluble flavonoids, quercetin and rutin.…”

Scientific Advances with Aspergillus Species that Are Used for Food and Biotech Applications

“…The available genome sequence enables identification of genes and functionally important regions of the genome. It has directed the research focus towards the development of genome-wide analysis methods for exploiting that information 2,23,24) , also in relation to fungal product formation and protein secretion 6,35,41) .…”