Aspergillus oryzae has been used in Japanese traditional foods industry, and it produces a copious amount of amylolytic enzymes such as alpha-amylase, glucoamylase, and alpha-glucosidase. These amylolytic genes are regulated by a transcriptional activator, AmyR, in the presence of starch or malto-oligosaccharides including maltose. The amyR gene disruptant showed significantly poor growth on starch medium but showed normal growth on maltose medium, suggesting the existence of alternative maltose-utilizing enzymes whose expression might not be regulated by AmyR. We have found a gene cluster highly homologous to the yeast maltose-utilizing MAL cluster by gene mining in A. oryzae EST and genome databases. This cluster consists of MAL61 homolog (designated malP), MAL62 homolog (designated malT), and MAL63 homolog (designated malR), and thus is designated MAL cluster in A. oryzae. Complementation of yeast mal61 showed that malP encodes a functional maltose permease. The purpose of this study is to elucidate the expression and function of MAL cluster genes. Northern analyses showed that malP and malT were expressed at high level in the presence of maltose but malR was expressed constitutively. Disruption of malR resulted in the loss of expression of malP and malT. These results indicated that MalR is required for gene expression of malP and malT at post-translational level. The malP or malR disruptant showed poor growth on maltose as well as on starch, comparable to the amyR disruptant, suggesting that malP and malR are somehow involved in assimilating starch. Alphaamylase activities of both disruptants were significantly low compared with those of wild type at early stage of maltose induction, and they were increasing gradually at late stages of induction. The result suggested that maltose transported into cell mainly by maltose permease encoded by malP is required for AmyR activation and resulting induction of amylolytic enzymes. Expression profiles of the malP and malR disruptants using A. oryzae microarrays will be reported.
Full conference title:
9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 9th (2008)