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Role of the regulatory gene areA of Aspergillus oryzae in nitrogen metabolism.

ABSTRACT: The areA gene of Aspergillus oryzae was cloned by cross-hybridization with the Aspergillus nidulans areA gene and was found to encode an 866-amino-acid protein that is very similar to other fungal nitrogen regulatory proteins. The A. oryzae areA gene can complement A. nidulans areA loss-of-function mutations. Functional analyses indicated that the N-terminal region of the A. oryzae AreA protein was dispensable for function and revealed a probable acidic activation domain in the protein. C-terminal truncation of the protein resulted in derepression of several nitrogen-controlled activities in A. nidulans, while deletions extending into the conserved GATA type zinc finger region abolished the activator function. The A. oryzae areA gene was inactivated by replacement with the A. oryzae pyrG gene. Strains containing the resulting areA deletion grew as well as the wild-type strain on glutamine but were unable to grow vigorously on other nitrogen sources, including ammonium. While A. oryzae exhibited reduced growth on 10 mM ammonium, the results of growth tests indicated that areA mutants of both A. oryzae and A. nidulans were affected in utilization of low concentrations of ammonium. The levels of the major nitrogen assimilatory enzymes, NADP-linked glutamate dehydrogenase (EC 1.4.1.4) and glutamine synthetase (EC 6.3.1.2), were determined. In both A. oryzae and A. nidulans areA mutants, the NADP-glutamate dehydrogenase levels were reduced, whereas the glutamine synthetase levels were not affected. These results suggest that the AreA protein may play an important role in the regulation of nitrogen assimilation in addition to its previously established regulatory role in nitrogen catabolism.

SUBMITTER: Christensen T

PROVIDER: S-EPMC106715 | biostudies-literature | 1998 Sep

REPOSITORIES: biostudies-literature

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Role of the regulatory gene areA of Aspergillus oryzae in nitrogen metabolism.

Christensen T T Hynes M J MJ Davis M A MA

Applied and environmental microbiology 19980901 9

The areA gene of Aspergillus oryzae was cloned by cross-hybridization with the Aspergillus nidulans areA gene and was found to encode an 866-amino-acid protein that is very similar to other fungal nitrogen regulatory proteins. The A. oryzae areA gene can complement A. nidulans areA loss-of-function mutations. Functional analyses indicated that the N-terminal region of the A. oryzae AreA protein was dispensable for function and revealed a probable acidic activation domain in the protein. C-termin ...[more]

PMID: 9726865

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Project description:Flagellin glycosylation plays a crucial role in flagellar assembly, motility and virulence in several pathogenic bacteria. However, little is known about the genetic determinants and biological functions of flagellin glycosylation in Xanthomonas oryzae pv. oryzae (Xoo), the causal pathogen of bacterial blight of rice. Here, the structure, regulation and functions of a ten-gene cluster gigX (glycosylation island genes of Xoo), which was embedded in a flagellar regulon, were characterized. gigX1 to gigX10 encoded putative enzymes or proteins involved in glycan biosynthesis and transfer, including a nucleotide sugar transaminase, an acyl-carrier protein (ACP), a 3-oxoacyl-ACP synthase, a 3-oxoacyl-ACP reductase, a dehydrogenase, an acetyltransferase, a ring hydroxylating dioxygenase, a hypothetical protein, a methyltransferanse and a glycosyltransferase, respectively. The gigX genes were co-transcribed in an operon and up-regulated by the upstream σ54 factor RpoN2 and transcriptional activator FleQ. In-frame deletion of each gigX gene affected flagellin glycosylation modification, meaning that the unglycosylated flagellin of the mutants was smaller than the glycosylated flagellin of the wild-type. No significant changes in flagellar filament and motility were observed in the ΔgigX mutants, among which only ΔgigX6 displayed increased swimming ability. Importantly, all mutants, except ΔgigX9, showed significantly increased virulence and bacterial growth in the susceptible rice cultivar IR24, and ΔgigX1 and ΔgigX10 showed enhanced type III secretion system (T3SS)-related gene expression. Moreover, the glycosylated flagellin of the wild-type induced higher H2 O2 levels in rice leaves than did the unglycosylated flagellins of ΔgigX1 or ΔgigX10. Taken together, this study reveals that the gigX cluster determines flagellin glycosylation, and implicates the regulatory role of post-translational modification with the glycosylation, acetylation and methylation of flagellin in the regulation of motility and virulence of Xoo.

Dataset Information

Role of the regulatory gene areA of Aspergillus oryzae in nitrogen metabolism.

Publications

Role of the regulatory gene areA of Aspergillus oryzae in nitrogen metabolism.

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