Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2010
Publication Date: February 12, 2011
Citation: Choi, Y., Goodwin, S.B. 2011. Gene encoding a C-type cyclin in Mycosphaerella graminicola is involved in aerial mycelium formation, filamentous growth, hyphal swelling, melanin biosynthesis, stress response, and pathogenicity. Molecular Plant-Microbe Interactions. 24:469-477. Interpretive Summary: Mycosphaerella graminicola is a fungal pathogen causing septoria tritici blotch, one of the most important diseases of wheat worldwide. Devising an efficient strategy to control M. graminicola has been hampered by our limited understanding of the molecular mechanisms by which it causes disease. Genes for c-type cyclins have been shown to be important for pathogenicity in other fungi, but whether they are important for infection by M. graminicola on wheat remains unknown. To test whether these genes are important in pathogenicity of M. graminicola, the gene for a c-type cyclin MCC1 was identified in the genomic sequence, cloned and interrupted to knock out its function. Four independent MCC1 knock-out mutants were generated by introducing defective copies of this gene using the bacterium Agrobacterium tumefaciens. All of the MCC1 knock-out mutants showed consistent multiple phenotypes, including reductions in radial growth, lowered production of aerial growths, delayed filamentous growth, unusual swellings of fungal hyphae, increased production of the dark pigment melanin, and increased stress tolerance. Furthermore, all of the mutants were reduced significantly in pathogenicity. These results indicate that the MCC1 gene is involved in multiple signaling pathways including those involved in pathogenicity in M. graminicola. Therefore, any chemicals that disrupt the function of this gene could be useful as potential fungicides. This information will be useful to fungal geneticists and evolutionary biologists to better understand the genetics and evolution of M. graminicola. Plant pathologists may be able to use this information to design better strategies for disease management, particularly once the biochemical basis for the major phenotypes is better understood.
Technical Abstract: Mycosphaerella graminicola is an important wheat pathogen causing septoria tritici blotch. To date, an efficient strategy to control M. graminicola has not been developed. More significantly, we have a limited understanding of the molecular mechanisms of M. graminicola pathogenicity. In this study, we attempted to characterize an MCC1-encoding c-type cyclin, a gene homologous to FCC1 in Fusarium verticillioides. Four independent MCC1 knock-out mutants were generated via Agrobacterium tumefaciens-mediated transformation. All of the MCC1 mutants showed consistent multiple phenotypes. Significant reductions in radial growth on PDA were observed in all of the MCC1 mutants. In addition, MCC1 gene-deletion mutants produced less aerial mycelium on PDA, showed delayed filamentous growth, had unusual hyphal swellings, produced more melanin, showed an increase in their stress tolerance response, and were reduced significantly in pathogenicity. These results indicate that the MCC1 gene is involved in multiple signaling pathways including those involved in pathogenicity in M. graminicola.