Catalase overexpression reduces the germination time and increases the pathogenicity of the fungus Metarhizium anisopliae

Abstract

Catalases and peroxidases are the most important enzymes that degrade hydrogen peroxide into water and oxygen. These enzymes and superoxide dismutase are the first lines of cell defense against reactive oxygen species. Metarhizium anisopliae displays an increase in catalase-peroxidase activity during germination and growth. To determine the importance of catalase during the invasion process of M. anisopliae, we isolated the cat1 gene. cat1 cDNA expression in Escherichia coli and the subsequent purification of the protein confirmed that the cat1 gene codes for a monofunctional catalase. Expression analysis of this gene by RT-PCR from RNA isolated from fungus grown in liquid cultures showed a decrease in the expression level of the cat1 gene during germination and an increase during mycelium growth. The expression of this gene in the fungus during the infection process of the larvae of Plutella xylostella also showed a significant increase during invasive growth. Transgenic strains overexpressing the cat1 gene had twice the catalase activity of the wild-type strain. This increase in catalase activity was accompanied by a higher level of resistance to exogenous hydrogen peroxide and a reduction in the germination time. This improvement was also observed during the infection of P. xylostella larvae. M. anisopliae transgenic strains overexpressing the cat1 gene grew and spread faster in the soft tissue of the insect, reducing the time to death of the insect by 25% and the dose required to kill 50% of the population 14-fold.

Oxygen‐rich culture conditions enhance the conidial infectivity and the quality of two strains of Isaria fumosorosea for potentially improved biocontrol processes

“…Previous reports established a close relation between the infectivity of entomopathogenic fungi and antioxidant enzymes. Morales‐Hernández et al found that overexpression of the catalase gene cat1 improved the infectivity of M. anisopliae , in addition to faster germination and higher tolerance to hydrogen peroxide. Recently, Wang et al determined the role of five catalase genes in B. bassiana ; the infectivity diminished after the knock‐out of genes catA , catP or catD ; also, these enzymes were linked to thermal tolerance and resistant to UV‐B radiation.…”

“…The exposure of an organism to sublethal stress increases the capacity for resistance not only to that particular type of stress but also to other stresses of a different nature (cross‐protection) . In this context, some reports have determined the role of antioxidant enzymes, mainly superoxide dismutases and catalases, in fungi during hyperoxidant states, and also as a response to different types of stress, which in turn is associated with improved infectivity …”

Antioxidant enzyme influences germination, stress tolerance, and virulence of Isaria fumosorosea

“…Similar results were also observed by Morales Hernandez et al . who observed that over expression of cat1 could be responsible for the germination of M. anisopliae mutant 13–19% faster than the wild type. The transgenic strains overexpressing the cat1 gene had twice the catalase activity of the wild‐type strain, in accord with the extra copy of the gene which is detected in both transgenic samples tested.…”

Transcriptome of an entomophthoralean fungus (Pandora formicae) shows molecular machinery adjusted for successful host exploitation and transmission

“…In this phase the fungus needs specific proteases able to digest the protein matrix in the host cuticle. Catalase, a detoxifying enzyme able to degrade hydrogen peroxide, plays an important role both in stress tolerance (protection against host oxidative defenses) and growth of entomopathogenic fungi (Morales Hernandez et al, 2010).…”