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Title: The Vayg1 gene controls microsclerotia development and melanin production in Verticillium dahliae

item FAN, RONG - Northwest Agricultural & Forestry University
item Klosterman, Steven
item WANG, CONGHAO - Northwest Agricultural & Forestry University
item SUBBARAO, KRISHNA - University Of California
item XU, X - Northwest Agricultural & Forestry University
item SHANG, WENJING - Northwest Agricultural & Forestry University
item HU, XIAOPING - Northwest Agricultural & Forestry University

Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2016
Publication Date: 1/1/2017
Citation: Fan, R., Klosterman, S.J., Wang, C., Subbarao, K.V., Xu, X., Shang, W., Hu, X. 2017. The Vayg1 gene controls microsclerotia development and melanin production in Verticillium dahliae. Fungal Genetics and Biology. 98:1–11.

Interpretive Summary: Verticillium dahliae is a soilborne plant pathogenic fungus and a cause of Verticillium wilt diseases of plants. Verticillium dahliae causes disease on over 200 plant species worldwide, including many agriculturally important crops. In addition to having a very broad host range, one of the reasons that V. dahliae is so difficult to control is because the fungus produces pigmented (melanized) resting structures that can survive in the soil for years. Therefore, a cultural practice of crop rotation is ineffective. The resting structures produced by V. dahliae are called microsclerotia, and there is not much known on the genetic basis of how the microsclerotia are formed. The pigment produced in maturing microsclerotia also contributes to the long term survival of the pathogen. The Vayg1 gene of V. dahliae was previously identified as strongly expressed in microsclerotia-producing cultures of a lettuce pathogen of V. dahliae, but not in cultures of V. dahliae that lacked microsclerotia. In this study, the gene Vayg1 was deleted in V. dahliae to gain insight on the function of Vayg1. The Vayg1 mutant strain could not produce microsclerotia, and also did not produce pigment. Furthermore the strain displayed reduced virulence on cotton. Insights into the genes necessary for pigment synthesis and microsclerotia formation in V. dahliae may lead to alternative control approaches to combat this fungus in the soil.

Technical Abstract: The fungus Verticillium dahliae causes plant vascular diseases on economically important crops and ornamental plants worldwide. This fungus produces darkly pigmented resting structures known as microsclerotia, which are able to survive for years in the soil, and represent a one of the defining characteristic of this species. The pigment produced in V. dahliae is the dihydroxynaphthalene (DHN)-melanin type, a form of melanin common among fungi, and named for the end product of this melanin biosynthetic pathway. In this study, we characterized the function of the V. dahliae Vayg1 gene, encoding a putative enzyme that catalyzes a step of the DHN-melanin biosynthetic pathway, based upon the known role of the homolog Ayg1 from Aspergillus fumigatus. Consistent with a role in DHN-melanin biosynthesis, the deletion ('Vayg1) strain of V. dahliae lost the ability to produce melanin. Intriguingly, however, the 'Vayg1 strain also lost the ability to produce microsclerotia. Additionally, the 'Vayg1 strain exhibited defects in radial growth rate, sporulation, pathogenicity, and oxidative stress resistance. Since these results revealed that the Vayg1 gene is necessary in V. dahliae for DHN-melanin and microsclerotia production, the Vayg1 product may catalyze a reaction involving a common precursor that affects both downstream biological synthesis of both DHN-melanin synthesis and microsclerotia production in V. dahliae.