Verticillium dahliae is a plant pathogenic fungus that reproduces asexually and its population structure is highly clonal. In the present study, 78 V. dahliae isolates from Iran were genotyped for mating type, single nucleotide polymorphisms (SNPs), and microsatellites to assign them to clonal lineages and to determine population genetic structure in Iran. The mating type of all isolates was MAT1-2. Based on neighbor-joining analysis and minimum spanning networks constructed from SNPs and microsatellite genotypes, respectively, all but four isolates were assigned to lineage 2B⁸²⁴; four isolates were assigned to lineage 4B. The inferred coalescent genealogy of isolates in lineage 2B⁸²⁴ showed a clear divergence into two clades that corresponded to geographic origin and host. Haplotypes of cotton and pistachio isolates sampled from central Iran were in one clade, and those of isolates from Prunus spp. sampled from northwestern Iran were in the other. The strong divergence in haplotypes between the two clades suggests that there were at least two separate introductions of lineage 2B⁸²⁴ to different parts of Iran. Given the history of cotton and pistachio cultivation and Verticillium wilt in Iran, these results are consistent with the hypothesis that cotton was historically a likely source inoculum causing Verticillium wilt in pistachio.

Terpenes constitute a major part of secondary metabolites secreted by plants in the rhizosphere. However, their specific functions in fungal–plant interactions have not been investigated thoroughly. In this study we investigated the role of monoterpenes in interactions between oilseed rape (Brassica napus) and the soilborne pathogen Verticillium longisporum. We identified seven monoterpenes produced by B. napus, and production of α‐pinene, β‐pinene, 3‐carene, and camphene was significantly increased upon fungal infection. Among them, β‐pinene was chosen for further analysis. Transcriptome analysis of V. longisporum on exposure to β‐pinene resulted in identification of two highly expressed pleotropic drug transporters paralog genes named VlAbcG1a and VlAbcG1b. Overexpression of VlAbcG1a in Saccharomyces cerevisiae increased tolerance to β‐pinene, while deletion of the VlAbcG1a homologous gene in Verticillium dahliae resulted in mutants with increased sensitivity to certain monoterpenes. Furthermore, the VlAbcG1a overexpression   strain displayed an increased tolerance to β‐pinene and increased virulence in tomato plants. Data from this study give new insights into the roles of terpenes in plant–fungal pathogen interactions and the mechanisms fungi deploy to cope with the toxicity of these secondary metabolites.

Phospholipase A ₂ (PLA ₂ ) is a lipolytic enzyme that hydrolyses phospholipids in the cell membrane. In the present study, we investigated the role of secreted PLA ₂ (VlsPLA ₂ ) in Verticillium longisporum , a fungal phytopathogen that mostly infects plants belonging to the Brassicaceae family, causing severe annual yield loss worldwide. Expression of the VlsPLA ₂ gene, which encodes active PLA ₂ , is highly induced during the interaction of the fungus with the host plant Brassica napus . Heterologous expression of VlsPLA ₂ in Nicotiana benthamiana resulted in increased synthesis of certain phospholipids compared to plants in which enzymatically inactive PLA ₂ was expressed (VlsPLA ₂ ^ΔCD ). Moreover, VlsPLA ₂ suppresses the hypersensitive response triggered by the Cf4/Avr4 complex, thereby suppressing the chitin‐induced reactive oxygen species burst. VlsPLA ₂ ‐overexpressing V. longisporum strains showed increased virulence in Arabidopsis plants, and transcriptomic analysis of this fungal strain revealed that the induction of the gene contributed to increased virulence. VlsPLA ₂ was initially localized to the host nucleus and then translocated to the chloroplasts at later time points. In addition, VlsPLA ₂ bound to the vesicle‐associated membrane protein A (VAMPA) and was transported to the nuclear membrane. In the nucleus, VlsPLA ₂ caused major alterations in the expression levels of genes encoding transcription factors and subtilisin‐like proteases, which play a role in plant immunity. In conclusion, our study showed that VlsPLA ₂ acts as a virulence factor, possibly by hydrolysing host nuclear envelope phospholipids, which, through a signal transduction cascade, may suppress basal plant immune responses.

Russian olive, also known as, Persian olive or oleaster (Elaeagnus angustifolia L.) is a species in the Elaeagnaceae family native to western and central Asia. In some orchards in Iran, intercroppi...

Phospholipases A ₂ (PLA ₂ ) are lipolytic enzymes, responsible for phospholipids hydrolysis. The role of PLA ₂ in various aspects of cell physiology has been shown, but their involvement in host-microbe interactions remains to be elucidated. The present study investigated the biological function of the secreted VIsPLA ₂ phospholipase in the phytopathogenic fungus Verticillium longisporum with emphasis on its role in host-microbe interactions. The VlsPLA ₂ was highly induced in V. longisporum during interaction with host plant Brassica napus , encoding an active phospholipase A ₂ . VlsPLA ₂ -overexpression V. longisporum strain showed an increased virulence on Arabidopsis plants, plausibly by inducing virulence factors. Furthermore, VIsPLA ₂ are transported to the nucleus, by hijacking VAMPA proteins, causing suppression of PTI-induced hypersensitive response, possibly by modulating the expression of genes involved in plant immunity. In summary, VlsPLA ₂ acts as a virulence factor by hydrolyzing the hosts nuclear envelope phospholipids, an action that induces signaling cascade, suppressing basal plant immunity responses.