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Characterization and expression analysis of a maltose-utilizing (MAL) cluster in Aspergillus oryzae
Sachiko Hasegawa1, Masahiro Takizawa, Haruhiko Suyama
1Laboratory of Bioindustrial Genomics, Department of Bioindustrial Informatics and Genomics, Graduate School of Agricultural Science, Tohoku University, Aoba-ku, Sendai 981-8555, Japan.
Aspergillus oryzae utilizes maltose via a newly identified MAL gene cluster, independent of the previously known amyR system. This discovery reveals a distinct pathway for maltose assimilation in this fungus.
Area of Science:
- Microbiology
- Molecular Biology
- Enzymology
Background:
- Starch and maltooligosaccharides induce amylolytic enzymes in Aspergillus oryzae.
- The transcriptional activator gene amyR is crucial for maltose induction of these enzymes.
- A previous study indicated an amyR-independent maltose utilization system in A. oryzae.
Purpose of the Study:
- To identify and characterize the A. oryzae gene cluster responsible for maltose assimilation.
- To elucidate the regulatory mechanism of maltose utilization in A. oryzae.
Main Methods:
- Genome analysis to identify MAL cluster homologs.
- Gene cloning, overexpression, and disruption.
- Enzyme activity assays (alpha-glucosidase).
- Growth analysis on various carbon sources.
Main Results:
- A MAL gene cluster homologous to Saccharomyces cerevisiae MAL cluster (malP, malT, malR) was identified in A. oryzae.
- Overexpression of malT increased alpha-glucosidase activity; malP enabled growth on maltose in S. cerevisiae.
- malP and malT expression were upregulated by maltose, while malR was constitutive.
- Disruption of malR or malP led to impaired maltose utilization and growth defects.
Conclusions:
- The identified MAL cluster (malP, malT, malR) is essential for maltose assimilation in Aspergillus oryzae.
- This system represents a distinct pathway for maltose utilization, separate from the amyR-controlled system.
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