Posttranscriptional control mediates cell type-specific localization of catalase A during Aspergillus nidulans development

• Published in: Journal of Bacteriology Vol. 180; no. 21; pp. 5733 - 5738
• Main Authors: Navarro, R.E, Aguirre, J
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.11.1998
• Subjects: Artificial Gene Fusion; ascospores; Aspergillus nidulans; Aspergillus nidulans - enzymology; Aspergillus nidulans - genetics; Aspergillus nidulellus; Bacteriology; Base Sequence; beta-galactosidase; catalase; Catalase - genetics; conidia; conidiation; conidiophores; cytochemistry; DNA, Bacterial; enzyme activity; enzymology; Eukaryotic Cells; fungal anatomy; Fungi; gene expression; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes; genetics; hyphae; Lac Operon; messenger RNA; metulae; Molecular biology; Molecular Sequence Data; osmotic pressure; phialides; Plant reproduction; promoter regions; Protein Biosynthesis; recombinant DNA; reporter genes; RNA Processing, Post-Transcriptional; RNA, Messenger; Spores, Bacterial; sporulation; stress; translation
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/JB.180.21.5733-5738.1998

Two differentially regulated catalase genes have been identified in the fungus Aspergillus nidulans. The catA gene belongs to a class whose transcripts are specifically induced during asexual sporulation (conidiation) and encodes a catalase accumulated in conidia. Using a developmental mutant affected in the brlA gene, which is unable to form conidia but capable of producing sexual spores (ascospores), we demonstrated that the catA mRNA accumulated during induction of conidiation but did not produce CatA protein. In contrast, high levels of catalase A activity were detected in the ascospores produced by this mutant, indicating that the catA gene is posttranscriptionally regulated. The same type of regulation was observed for a catA::lacZ translational gene fusion, suggesting that the catA message 5' untranslated region could be involved in translational control during development. In a wild-type strain, beta-galactosidase activity driven from the catA::lacZ gene fusion was low in hyphae and increased 50-fold during conidiation and 620-fold in isolated conidia. Consistent with this finding spatial expression of the reporter gene was restricted to metulae, phialides, and conidia. Conidium-associated expression was maintained in a stuA mutant, in which the conidiophore cell pattern is severely deranged. catA mRNA accumulation was also observed when vegetative mycelia was subject to oxidative, osmotic, and nitrogen or carbon starvation stress. Nevertheless, catalase A activity was restricted to the conidia produced under nutrient starvation. Our results provide support for a model in which translation of the catA message, accumulated during conidiation or in response to different types of stress, is linked to the morphogenetic processes involved in asexual and sexual spore formation. Our findings also indicate that brlA-independent mechanisms regulate the expression of genes encoding spore-specific products.