Multiple Catalase Genes Are Differentially Regulated in Aspergillus nidulans

Abstract

Detoxification of hydrogen peroxide is a fundamental aspect of the cellular antioxidant responses in which catalases play a major role. Two differentially regulated catalase genes, catA and catB, have been studied in Aspergillus nidulans. Here we have characterized a third catalase gene, designated catC, which predicts a 475-amino-acid polypeptide containing a peroxisome-targeting signal. With a molecular mass of 54 kDa, CatC shows high similarity to other small-subunit monofunctional catalases and is most closely related to catalases from other fungi, Archaea, and animals. In contrast, the CatA (ϳ84 kDa) and CatB (ϳ79 kDa) enzymes belong to a family of large-subunit catalases, constituting a unique fungal and bacterial group. The catC gene displayed a relatively constant pattern of expression, not being induced by oxidative or other types of stress. Targeted disruption of catC eliminated a constitutive catalase activity not detected previously in zymogram gels. However, a catalase activity detected in catA catB mutant strains during late stationary phase was still present in catC and catABC null mutants, thus demonstrating the presence of a fourth catalase, here named catalase D (CatD). Neither catC nor catABC triple mutants showed any developmental defect, and both mutants grew as well as wild-type strains in H 2 O 2 -generating substrates, such as fatty acids, and/or purines as the sole carbon and nitrogen sources, respectively. CatD activity was induced during late stationary phase by glucose starvation, high temperature, and, to a lesser extent, H 2 O 2 treatment. The existence of at least four differentially regulated catalases indicates a large and regulated capability for H 2 O 2 detoxification in filamentous fungi.Several studies indicate that reactive oxygen species play crucial roles in various aspects of cell physiology, such as cellular defense (45), life span (38), stress signaling (22), development (19), apoptosis (30), and pathology (33). The hydrogen peroxide formed during aerobic metabolism is capable of generating other reactive oxygen species, which can damage many cellular components (18). Catalases and peroxidases are the most important enzymatic systems used to degrade H 2 O 2 . There are three separate families of catalases: Mn-catalases, bifunctional catalase-peroxidases, and monofunctional, or "true," catalases. The last group is the one best characterized and corresponds to homotetrameric heme-containing enzymes present in eubacteria and eukaryotes and recently also found in the Archaea (34). Within this family of catalases, two clearly distinct classes can be recognized: the small-subunit (50-to 65-kDa) and the large-subunit (ϳ80-kDa) enzymes. The first class includes a large number of catalases from bacteria, plants, fungi, and animals. An increasing number of catalases of the second class have been identified in bacteria and filamentous fungi (5,8,13,15,(23)(24)(25)27, 37) but not in higher eukaryotes.The core sequence of the true catalases is composed of 360 to 390 amino acid resid...

Investigating Aspergillus nidulans secretome during colonisation of cork cell walls

“…[46]) has been implicated in the detoxification of hydrogen peroxide, thus strongly associated with growing and developing hyphae [59]. Its identification in the cork secretome (8 protein spots) supports the idea that A. nidulans was actively growing on cork until the end of the incubation.…”

The response of the Rhizobium leguminosarum bv. trifolii wild-type and exopolysaccharide-deficient mutants to oxidative stress

“…Also for the Rt2472 mutant, differences in the CAT activity for these two techniques were found. This phenomenon is difficult to explain clearly, but similar differences between native gel detection and spectrophotometric measurement of the CAT activity were presented in several reports concerning various organisms such as Saccharomyces, Neurospora crassa, Aspergillus nidulans, and maize (Gamero-Sandemetrio et al 2013;Schliebs et al 2006;Wadsworth and Scandalios 1990;Kawasaki and Aguirre 2001). Moreover, Gamero-Sandemetrio et al (2013) observed similar discrepancy between zymogram and enzymatic assays for SOD activity in several S. cerevisiae strains, indicating that native gel detection cannot always be considered as a reliable quantitative technique.…”

Redundancy, phylogeny and differential expression of Histoplasma capsulatum catalases The GenBank accession numbers for the cDNA sequences reported in this paper are AF139985 (CATB), AF189368 (CATA) and AF189369 (CATP).

“…The multiple catalase genes of both Neurospora crassa and Emericella nidulans are differentially expressed during oxidative stress and development (Chary & Natvig, 1989 ;Kawasaki et al, 1997 ;Kawasaki & Aguirre, 2001 Fig. 5, CATA RNA abundance showed a marked increase after H # O # challenge.…”

“…Since then, a CATP-homologous gene from Emericella nidulans (Ascomycota ; subphylum Pezizomycotina), termed CATC, was identified (Kawasaki & Aguirre, 2001). In addition, we searched the unannotated sequence data from the Cryptococcus neoformans (phylum Basidiomycota) and Neurospora crassa (Ascomycota ; subphylum Pezizomycotina) genome projects.…”