The bZip transcription factor VdMRTF1 is a negative regulator of melanin biosynthesis and virulence in Verticillium dahliae

Authors: LAI, MEIJUN - Beijing Forestry University; CHENG, ZHUO - Beijing Forestry University; XIAO, LUYAO - Beijing Forestry University; Klosterman, Steven; WANG, YONGLIN - Beijing Forestry University

Submitted to: Microbiology Spectrum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2022
Publication Date: 4/11/2022
Citation: Lai, M., Cheng, Z., Xiao, L., Klosterman, S.J., Wang, Y. 2022. The bZip transcription factor VdMRTF1 is a negative regulator of melanin biosynthesis and virulence in Verticillium dahliae. Microbiology Spectrum. 10(2). Article e02581-21. https://doi.org/10.1128/spectrum.02581-21.
DOI: https://doi.org/10.1128/spectrum.02581-21

Interpretive Summary: The plant pathogenic fungus Verticillium dahliae causes Verticillium wilt disease on over 400 plant species worldwide. Verticillium wilt is detrimental to numerous crop plants and ornamentals and also many trees. The fungus survives long term in soils by producing survival structures known as microslerotia, which are also heavily melanized. The microsclerotia germinate and infect plant roots. Melanization is known to contribute to the long-term survival of the microsclerotia. In this study, we identified a gene in V. dahliae encoding a protein that suppresses microsclerotia formation, melanin production, and virulence. The identification of the genes that control aspects of survival and virulence in V. dahliae may lead to new control measures directed at the fungus in the soil, and thus may block the pathogen prior to root infection.

Technical Abstract: The ascomycete fungus Verticillium dahliae infects over 400 plant species and causes serious losses of economically important crops, such as cotton and tomato, and also of woody plants, such as smoke tree, maple, and olive. Melanized long-term survival structures known as microsclerotia play crucial roles in the disease cycle of V. dahliae, enabling this soilborne fungus to survive for years in the soil in the absence of a host. Previously, we identified VdMRTF1 (microsclerotia-related transcription factor) encoding a bZip transcription factor which is downregulated during microsclerotial development in V. dahliae. In the present study, we showed that VdMRTF1 negatively controls melanin production and virulence by genetic, biological, and transcriptomic analyses. The mutant strain lacking VdMRTF1 ('VdMRTF1) exhibited increased melanin biosynthesis and the defect also promoted microsclerotial development and sensitivity to Ca2+. In comparison with the wild-type strain, the 'VdMRTF1 strain showed a significant enhancement in virulence and displayed an increased capacity to eliminate reactive oxygen species in planta. Furthermore, analyses of transcriptomic profiles between the 'VdMRTF1 and wild-type strains indicated that VdMRTF1 regulates the differential expression of genes associated with melanin biosynthesis, tyrosine metabolism, hydrogen peroxide catabolic processes, and oxidoreductase activity in V. dahliae. Taken together, these data show that VdMRTF1 is a negative transcriptional regulator of melanin biosynthesis, microsclerotia formation, and virulence in V. dahliae.