Prevalence and Strain Composition of Potato virus Y Circulating in Potato Fields in China's North-Central Province of Shanxi

Transcriptome analysis of the synergistic mechanisms between two strains of potato virus Y in Solanum tuberosum L

Many viruses employ a process known as superinfection exclusion (SIE) to block subsequent entry or replication of the same or closely related viruses in the cells they occupy. SIE is also referred to as Cross-protection refers to the situation where a host plant infected by a mild strain of a virus or viroid gains immunity against a more severe strain closely related to the initial infectant. The mechanisms underlying cross-protection are not fully understood. In this study, we performed a comparative transcriptomic analysis of potato (Solanum tuberosum L.) leaves. The strains PVYN-Wi-HLJ-BDH-2 and PVYNTN-NW-INM-W-369-12 are henceforth designated as BDH and 369, respectively. In total, 806 differentially expressed genes (DEGs) were detected between the Control and JZ (preinfected with BDH and challenge with 369) treatment. Gene Ontology (GO) analysis showed that the response to external biological stimulation, signal transduction, kinase, immunity, redox pathways were significantly enriched. Among these pathways, we identified numerous differentially expressed metabolites related to virus infection. Moreover, our data also identified a small set of genes that likely play important roles in the establishment of cross-protection. Specifically, we observed significant differential expression of the A1-II gamma-like gene, elongation factor 1-alpha-like gene, and subtilisin-like protease StSBT1.7 gene, with StSBT1.7 being the most significant in our transcriptome data. These genes can stimulate the expression of defense plant genes, induce plant chemical defense, and participate in the induction of trauma and pathogenic bacteria. Our findings provided insights into the mechanisms underlying the ability of mild viruses to protect host plants against subsequent closely related virus infection in Solanum tuberosum L.

Development of an attenuated potato virus Y mutant carrying multiple mutations in helper-component protease for cross-protection

Tobacco (Nicotiana tabacum) is one of the major cash crops in China. Potato virus Y (PVY), a representative member of the genus Potyvirus, greatly reduces the quality and yield of tobacco leaves by inducing veinal necrosis. Mild strain-mediated cross-protection is an attractive method of controlling diseases caused by PVY. Currently, there is a lack of effective and stable attenuated PVY mutants. Potyviral helper component-protease (HC-Pro) is a likely target for the development of mild strains. Our previous studies showed that the residues lysine at positions 124 and 182 (K124 and K182) in HC-Pro were involved in PVY virulence, and the conserved KITC motif in HC-Pro was involved in aphid transmission. In this study, to improve the stability of PVY mild strains, K at position 50 (K50) in KITC motif, K124, and K182 were separately substituted with glutamic acid (E), leucine (L), and arginine (R), resulting in a triple-mutant PVY-HCELR. The mutant PVY-HCELR had attenuated virulence and did not induce leaf veinal necrosis symptoms in tobacco plants and could not be transmitted by Myzus persicae. Furthermore, PVY-HCELR mutant was genetically stable after six serial passages, and only caused mild mosaic symptoms in tobacco plants even at 90 days post inoculation. The tobacco plants cross-protected by PVY-HCELR mutant showed high resistance to the wild-type PVY. This study showed that PVY-HCELR mutant was a promising mild mutant for cross-protection to control PVY.

Genome sequences of six recombinant variants of potato virus Y identified in North American potato cultivars grown in China

Six genome sequences for potato virus Y (PVY) recombinants are reported from two North American potato cultivars grown in China. The coding complete sequences encode a single open reading frame characteristic of potyviruses. The six sequenced PVY isolates represent three distinct recombinants of PVY, namely N-Wi, SYR-I, and SYR-II.