Molecular Pathogens, 2025, Vol.16, No.2, 77-86 http://microbescipublisher.com/index.php/mp 78 2 Major Pathogens Affecting Grapevine 2.1 Fungal pathogens Downy mildew is prone to occur in humid climates. Its pathogen is called Plasmopara viticola, which is very harmful to the vines. This pathogen will send some special substances (called “effectors’) into the grape cells to interfere with the grape’s immune response. One of the effects called PvAvh77 is particularly critical. On the one hand, it can trigger cell death and activate the defensive response of grapes; on the other hand, it may also affect the gene regulatory network within grapes, weakening some immune signals, so that bacteria can easily avoid defense (Figure 1) (Fu et al., 2023). Research has found that a transcription factor called VvWRKY33 is important in combating P. viticola. It can open up some genes related to immunity and make grapes more resistant. To improve the disease resistance of grapes, breeders have introduced some resistance loci (such as Rpv3, Rpv10 and Rpv12) into grape varieties. Doing so can reduce dependence on fungicides (Nascimento-Gavioli et al., 2017; Wingerter et al., 2021). Figure 1 PvAvh77 requires nuclear localization to trigger cell death (Adopted from Fu et al., 2023) Image caption: PvAvh77, PvAvh77-M2 (truncated PvAvh77 without signal peptide and RxLR-dEER motif), PvAvh77NES (harbouring a Nuclear Export Signal), and PvAvh77nes (harbouring a non-functional nuclear export signal) were transiently expressed as GFP fusions with a PV40-NLS-mCherry marker in (A) ‘Beaumont’ and (B) N. benthamiana leaves to determine sub-cellular localization by confocal microscopy at 72~96 hpa and 36 hpa~48 hpa, respectively. GFP empty vector was used as control. The scale bar indicates (A) 20 μm and (B) 50 μm. (C) and (D) represent cell death assays in ‘Beaumont’ and N. benthamiana leaves, respectively, induced with PvAvh77, PvAvh77-M2, PvAvh77NES, or PvAvh77nes. Photographs of grapevine leaves were taken 7~10 dpa, and of N. benthamiana leaves 3~5 dpa. The scale bar indicates 1 cm. (E) Electrolyte leakage from the infiltrated leaf discs was monitored to quantify cell death. The data represent means ±SD based on three independent replicates, and asterisks indicate significant differences from the GFP control by one-way ANOVA followed by Tukey’s-b test (**P<0.01) (Adopted from Fu et al., 2023)
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