The transcription factor VdHapX controls iron homeostasis and is crucial for virulence in the vascular pathogen Verticillium dahliae

Authors: WANG, YONGLIN - Beijing Forestry University; DENG, CHENGLIN - Beijing Forestry University; TIAN, LONGYAN - Beijing Forestry University; XIONG, DIANGUANG - Beijing Forestry University; TIAN, CHENGMING - Beijing Forestry University; Klosterman, Steven

Submitted to: mSphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2018
Publication Date: 9/5/2018
Citation: Wang, Y., Deng, C., Tian, L., Xiong, D., Tian, C., Klosterman, S.J. 2018. The transcription factor VdHapX controls iron homeostasis and is crucial for virulence in the vascular pathogen Verticillium dahliae. mSphere. 3(5):e00400-18. https://doi.org/10.1128/mSphere.00400-18.
DOI: https://doi.org/10.1128/mSphere.00400-18

Interpretive Summary: Verticillium dahliae is a soilborne plant pathogenic fungus and a cause of Verticillium wilt diseases of plants. This fungus causes disease on well over 200 plant species worldwide, including many agriculturally important crops. In this study, we examined the function of a gene, known as VdHapX, thought to play a role in the acquisition and utilization of iron in V. dahliae. The VdHapX gene was deleted in the fungus and the growth and pathogenicity were examined relative to the original strain that had not been mutated. The results indicate that VdHapX in V. dahliae is required to produce normal levels of the long-lived survival structures of V. dahliae, known as microsclerotia. VdHapX is also required for protection against excess iron and oxidative stress, and is required for full virulence in the plant host studied. Insights into the genes necessary for survival and microsclerotia formation in V. dahliae may lead to alternative control approaches to eliminate the fungus or reduce it survival in the soil.

Technical Abstract: Iron homeostasis is essential for full virulence and viability in many pathogenic fungi. Here we showed that the bZip transcription factor VdHapx functions as a key regulator of iron homeostasis for adaptation to iron-depleted and iron-excess conditions, and is required for full virulence in the vascular wilt fungus Verticillium dahliae. Deletion of VdHapX impaired mycelial growth and conidiation under both iron starvation and sufficiency. Furthermore, disruption of VdHapX led to decreased formation of the long-lived survival structures of V. dahliae, known as microsclerotia. Expression of genes involved in iron-utilization pathways and siderophore biosynthesis was mis-regulated in the 'VdHapX strain in the iron-depleted condition. Additionally, the 'VdHapX strain exhibited increased sensitivity to high-iron concentrations and H2O2, indicating that VdHapX also contributes to iron or H2O2 detoxification. The 'VdHapX train showed a strong reduction in virulence on smoke tree (Cotinus coggygria), and was delayed in its ability to penetrate plant epidermis. This study demonstrated that VdHapX is a conserved protein that mediates adaptation to iron starvation and excesses, affects microsclerotia formation, and is crucial for virulence of V. dahliae.