Loss of Catalase-1 (Cat-1) results in decreased conidial viability enhanced by exposure to light in Neurospora crassa.

Light is one of the most important factors inducing morphogenesis in Neurospora crassa. The reception of light triggers the generation of reactive oxygen species (ROS) including hydrogen peroxide (H(2)O(2)). Catalase-1 (Cat-1) is one of three catalases known to detoxify H(2)O(2) into water and oxygen. We reported that the photomorphogenetic characteristics of mutants in nucleoside diphosphate kinase-1 (NDK-1), a light signal transducer, are severely affected, and NDK-1 interacted with Cat-1 in a yeast two-hybrid assay. To disclose the function of Cat-1, we created a Cat-1 loss-of-function mutant (cat-1 ( RIP )) by the repeat induced point-mutation (RIPing) method. No Cat-1 activity was detected in the mutant strain. Forty guanines were replaced with adenines in the cat-1 gene of cat-1 ( RIP ), which caused 30 amino acid substitutions. The mutant strain grew normally, but its conidia and mycelia were more sensitive to H(2)O(2) than those of the wild type. The lack of Cat-1 activity also caused a significant reduction in the conidial germination rate. Furthermore, light enhanced this reduction in cat-1 ( RIP ) more than that in the wild type. Introduction of cat-1 into the mutant reversed all of these defective phenotypes. These results indicate that Cat-1 plays an important role in supporting the survival of conidia under oxidative and light-induced stress.