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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR AND GENETIC MECHANISMS OF FUNGAL DISEASE RESISTANCE IN GRAIN CROPS Title: Mve1 Encoding the Velvet Gene Product Homolog in Mycosphaerella Graminicola Is Associated with Aerial Mycelium Formation, Melanin Biosynthesis, Hyphal Swelling, and Light Signaling

Authors
item Choi, Yoon-E
item Goodwin, Stephen

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2010
Publication Date: January 27, 2011
Citation: Choi, Y., Goodwin, S.B. 2011. MVE1 Encoding the velvet gene product homolog in Mycosphaerella graminicola is associated with aerial mycelium formation, melanin biosynthesis, hyphal swelling, and light signaling. Applied and Environmental Microbiology. 77:942-953.

Interpretive Summary: The fungus Mycosphaerella graminicola is an important pathogen of wheat that causes the disease septoria tritici blotch. Despite the serious impact of M. graminicola on wheat production worldwide, knowledge about its molecular biology is limited. The velvet gene is one of the key regulators of diverse cellular processes including development and secondary metabolism in many fungi. However, the species analyzed to date are not related to the Dothideomycetes, the largest class of plant-pathogenic fungi, and its function in this group is not known. To test the hypothesis that the velvet gene will have similar functional roles in the Dothideomycetes as it does in other fungi, a velvet gene was identified in M. graminicola. Eleven independent gene-deletion mutants were generated and all showed consistent phenotypes indicating the involvement of the velvet gene in multiple signaling pathways. The mutant strains showed albino phenotypes and less production of aerial growth on agar plates. In liquid culture, mutant strains showed curled growth and abnormal swelling. In addition, velvet gene deletion led to hypersensitivity to shaking, less water resistance, and blindness to light-dependent stimulation of aerial growth. However, pathogenicity to wheat was not altered. Our data suggest that the velvet gene plays crucial roles in multiple key signaling pathways and is associated with light signaling in M. graminicola. This information will be useful to fungal geneticists and evolutionary biologists to better understand M. graminicola and other Dothideomycetes. Plant pathologists may be able to use this information to design improved strategies for disease management, particularly once the biochemical basis for the observed changes is better understood.

Technical Abstract: The ascomycete fungus Mycosphaerella graminicola is an important pathogen of wheat that causes the disease septoria tritici blotch. Despite the serious impact of M. graminicola on wheat production worldwide, knowledge about its molecular biology is limited. The velvet gene, veA, is one of the key regulators of diverse cellular processes including development and secondary metabolism in many fungi. However, the species analyzed to date are not related to the Dothideomycetes, the largest class of plant-pathogenic fungi, and its function in this group is not known. To test the hypothesis that the velvet gene will have similar functional roles in the Dothideomycetes, a veA-homologous gene, MVE1, was identified in M. graminicola. Eleven independent MVE1 gene-deletion mutants ('mve1) were generated via Agrobacterium tumefaciens-mediated transformation. All of the MVE1 mutants showed consistent pleiotrophic phenotypes indicating the involvement of MVE1 in multiple signaling pathways. 'mve1 strains showed albino phenotypes with significant reductions in melanin biosynthesis and less production of aerial mycelia on agar plates. In liquid culture, 'mve1 strains showed abnormal hyphal swelling, which was suppressed completely by osmotic stress or under lower temperature. In addition, MVE1 gene deletion led to hypersensitivity to shaking, less hydrophobicity, and blindness to light-dependent stimulation of aerial mycelium production. However, pathogenicity was not altered in 'mve1 strains, so the light-signaling pathway associated with MVE1 does not appear to be important for septoria tritici blotch disease. Our data suggest that the MVE1 gene plays crucial roles in multiple key signaling pathways and is associated with light signaling in M. graminicola.

Last Modified: 11/23/2014
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