Vector Construction

All primers used in this study are listed in Supplementary Table S1. A schematic diagram of the vector constructs is shown in Supplementary Figure S1. The PvAvh74 gene was amplified from genomic DNA from P. viticola isolate “YL” (Yin et al., 2017). For the PVX assay, PvAvh74 without the predicted signal peptide and PvAvh74 deletion mutants were cloned and subsequently ligated into the SmaI and NotI restriction enzyme sites of the pGR107 vector. The nuclear export signal (NES) sequence and corresponding mutated sequence (nes) (Wen et al., 1995) were extended to the carboxyl (C) terminus of PvAvh74 using overhanging primers (Supplementary Table S1). Then, PvAvh74, PvAvh74^NES, and PvAvh74^nes were ligated into the pCAMBIA2300-GFP vector cut using appropriate restriction enzymes. For the virus-induced gene silencing (VIGS) assay, fragments of target genes were amplified and fused into the EcoRI and BamHI restriction enzyme sites of the pTRV2 vector. To confirm the secretion function of the PvAvh74 signal peptide, the sequence was cloned and then introduced into pSUC2T7M13ORI (pSUC2) (Jacobs et al., 1997) cut using EcoRI and XhoI restriction sites.