ZafA‐mediated regulation of zinc homeostasis is required for virulence in the plant pathogen Fusarium oxysporum

Abstract

During infection, soilborne fungal pathogens face limiting conditions of different metal ions, including zinc. The role of zinc homeostasis in fungal pathogenicity on plants remains poorly understood. Here it is shown that the transcription factor ZafA, orthologous to Saccharomyces cerevisiae Zap1, functions as a key regulator of zinc homeostasis and virulence in Fusarium oxysporum, a cross-kingdom pathogen that causes vascular wilt on more than 100 plant species and opportunistic infections in humans. Expression of zafA is induced under zinc-limiting conditions and repressed by zinc. Interestingly, zafA is markedly up-regulated during early stages of plant infection, suggesting that F. oxysporum must cope with limited availability of zinc. Deletion of zafA results in deactivation of high-affinity zinc transporters, leading to impaired growth under zinc deficiency. Fusarium oxysporum strains lacking ZafA are reduced in their capability to invade and kill tomato plants and the non-vertebrate animal model Galleria mellonella. Collectively, the results indicate that ZafA-mediated adaptation to zinc deficiency is required for full virulence of F. oxysporum on plant and animal hosts. Rep, M. (2010) Comparative genomics reveals mobile pathogenicity chromosomes in Fusarium. Nature, 464, 367-373. Maret, W. (2013) Zinc biochemistry: from a single zinc enzyme to a key element of life. Adv. Nutr. 4, 82-91. Moreno, M.A., Ibrahim-Granet, O., Vicentefranqueira, R., Amich, J., Ave, P., Leal, F., Latgé, J.-P. and Calera, J.A. (2007) The regulation of zinc homeostasis by the ZafA transcriptional activator is essential for Aspergillus fumigatus virulence. Mol. Microbiol. 64, 1182-1197.

Fungal–Metal Interactions: A Review of Toxicity and Homeostasis

“…zrfD/E/H are not restricted by pH and can function in either acidic or alkaline environments [ 23 ]. In F. oxysporum , zrfA and zrfB are also zinc importers regulated by transcription factor ZafA [ 163 ]. During infection, ZafA allows F. oxysporum to adapt to a zinc-limiting environment, such as if the host enacts nutritional immunity to deprive it of this essential metal [ 163 ].…”

“…In F. oxysporum , zrfA and zrfB are also zinc importers regulated by transcription factor ZafA [ 163 ]. During infection, ZafA allows F. oxysporum to adapt to a zinc-limiting environment, such as if the host enacts nutritional immunity to deprive it of this essential metal [ 163 ]. Basidiomycetes have similar homology.…”

Current progress on pathogenicity‐related transcription factors in Fusarium oxysporum

“…In the C2H2 zinc finger domain, the presence of a zinc atom with two conserved cysteine residues at one end of the β‐sheet and two conserved histidine residues at the α‐helix C‐terminus ensure the stability of the zinc finger structure (Wolfe et al, 2000). In F. oxysporum , a total of five C2H2 ZFs have been identified and functionally tested, namely, PacC, ZafA, Ste12, FolCzf1, and Con7‐1 (Table 2) (Asuncion Garcia‐Sanchez et al, 2010; Caracuel et al, 2003; López‐Berges, 2020; Ruiz‐Roldan et al, 2015; Yun et al, 2019). GATA proteins, a family of GATA‐binding zinc finger transcription factors, play diverse functions in fungi and consist of one or two zinc‐binding modules with four cysteines embedded in the sequence Cys‐X2‐Cys‐X17/18‐Cys‐X2‐Cys and an adjacent basic region (Teakle & Gilmartin, 1998).…”

“…In Fol , ZAFA expression is induced under zinc‐limiting conditions and repressed by zinc at early stages of plant infection, which regulates the expression of many genes in response to zinc deficiency, including high‐affinity membrane zinc transporters, such as Zrt1, Zrt2, Zrt3, Fet4, and Zrc1 (López‐Berges, 2020). ZafA is also required for full virulence of Fol in plant and animal hosts (López‐Berges, 2020).…”

“…In Fol , ZAFA expression is induced under zinc‐limiting conditions and repressed by zinc at early stages of plant infection, which regulates the expression of many genes in response to zinc deficiency, including high‐affinity membrane zinc transporters, such as Zrt1, Zrt2, Zrt3, Fet4, and Zrc1 (López‐Berges, 2020). ZafA is also required for full virulence of Fol in plant and animal hosts (López‐Berges, 2020). In the opportunistic fungal pathogen A. fumigatus , the homolog of ZafA, AoZafA, also plays an essential role in maintaining zinc homeostasis, and AoZafA was found to be regulated by pH and influenced by the PacC transcriptional regulator (Amich et al, 2009, 2010).…”