The Helper Component Proteinase Cistron of Potato virus Y Induces Hypersensitivity and Resistance in Potato Genotypes Carrying Dominant Resistance Genes on Chromosome IV

Abstract

The Nc(tbr) and Ny(tbr) genes in Solanum tuberosum determine hypersensitive reactions, characterized by necrotic reactions and restriction of the virus systemic movement, toward isolates belonging to clade C and clade O of Potato virus Y (PVY), respectively. We describe a new resistance from S. sparsipilum which possesses the same phenotype and specificity as Nc(tbr) and is controlled by a dominant gene designated Nc(spl). Nc(spl) maps on potato chromosome IV close or allelic to Ny(tbr). The helper component proteinase (HC-Pro) cistron of PVY was shown to control necrotic reactions and resistance elicitation in plants carrying Nc(spl), Nc(tbr), and Ny(tbr). However, inductions of necrosis and of resistance to the systemic virus movement in plants carrying Nc(spl) reside in different regions of the HC-Pro cistron. Also, genomic determinants outside the HC-Pro cistron are involved in the systemic movement of PVY after induction of necroses on inoculated leaves of plants carrying Ny(tbr). These results suggest that the Ny(tbr) resistance may have been involved in the recent emergence of PVY isolates with a recombination breakpoint near the junction of HC-Pro and P3 cistrons in potato crops. Therefore, this emergence could constitute one of the rare examples of resistance breakdown by a virus which was caused by recombination instead of by successive accumulation of nucleotide substitutions.

Simultaneous Mutations in Multi-Viral Proteins Are Required for Soybean mosaic virus to Gain Virulence on Soybean Genotypes Carrying Different R Genes

“…Our data are consistent with recent findings that concurrent mutations of HC-Pro and P3 are required for G2 (the N isolate) to gain virulence on Rsv1 -genotype soybean [31], [43]. The HC-Pro of Potato virus Y (PVY) has been shown to act as a virulence determinant on potato ( Solanum tuberosum ) and S. sparsipilum containing PVY resistance genes Nc tbr and Nc spl , respectively [2]. In several other studies, HC-Pro was found to be involved in potyvirus symptom development [44]–[48].…”

“…The use of genetic resistance is considered the most effective and sustainable approach to the control of plant pathogens as it is environmentally-friendly and target-specific, and provides reliable protection without additional labor or material costs during the growing season [2], [3]. The major genetic resistance that has been extensively used in agriculture is mediated by R gene.…”

“…During the coevolutionary arms race of viral pathogens and their host plants, genetic diversity generated by spontaneous mutations (resulting from error-prone replication) and RNA recombination, and the selection force acting on this variability lead to the occurrence of resistance-breaking isolates [3], [8]–[10]. Molecular identification and characterization of virulent determinants from these isolates and their interactions with major resistance genes will advance knowledge of resistance durability, which is essential for developing and utilizing genetic resistance for crop protection [2], [7], [11].…”

Resistance to Viruses of Potato and their Vectors

“…S. tuberosum ssp andigena also was a source of a dominant HR gene for resistance to PVA (Ra adg ), as well as a source of a recessive resistance (ra) to systemic movement of PVA; both of these genes were linked to Ry adg on chromosome XI (Hämäläinen et al, 2000). Genes encoding an HR to PVY in potato (Ny tbr ) and in S. sparsipilum (Nc spl ) were found to be either allelic or map very close on chromosome IV (Moury et al, 2011).…”

RNA-Dependent RNA Polymerase (NIb) of the Potyviruses Is an Avirulence Factor for the Broad-Spectrum Resistance Gene Pvr4 in Capsicum annuum cv. CM334

“…For example, PVY VPg interacts with a recessive resistance protein, pvr2 in pepper which is also known as a member of eukaryotic initiation factor 4E (elF4E) [9]. Another PVY viral protein, HC-Pro is known to function broadly in potato and tobacco by interacting with elF4E and its elFiso4E [10], and is also involved in HR-like cell death in potato by responding to resistance genes called NC tbr , NC spl and Ny tbr [7]. A PVY protease, NIa protease (also called NIaPro) was found to be required for Ry -mediated resistance of potato against PVY [5].…”