ABSTRACT
The purpose of the study was to investigate the role of salicylic acid (SA) signalling in Ny-1-mediated hypersensitive resistance (HR) of potato (Solanum tuberosum L.) to Potato virus Y (PVY). The responses of the Ny-1 allele in the Rywal potato cultivar and transgenic NahG-Rywal potato plants that do not accumulate SA were characterized at the cytological, biochemical, transcriptome, and proteome levels. Analysis of noninoculated and inoculated leaves revealed that HR lesions started to develop from 3 d post inoculation and completely restricted the virus spread. At the cytological level, features of programmed cell death in combination with reactive oxygen species burst were observed. In response to PVY infection, SA was synthesized de novo. The lack of SA accumulation in the NahG plants led to the disease phenotype due to unrestricted viral spreading. Grafting experiments show that SA has a critical role in the inhibition of PVY spreading in parenchymal tissue, but not in vascular veins. The whole transcriptome analysis confirmed the central role of SA in orchestrating Ny-1-mediated responses and showed that the absence of SA leads to significant changes at the transcriptome level, including a delay in activation of expression of genes known to participate in defence responses. Moreover, perturbations in the expression of hormonal signalling genes were detected, shown as a switch from SA to jasmonic acid/ethylene signalling. Viral multiplication in the NahG plants was accompanied by downregulation of photosynthesis genes and activation of multiple energy-producing pathways.
Subject(s)
Plant Diseases/immunology , Plant Proteins/genetics , Potyvirus/physiology , Salicylic Acid/metabolism , Solanum tuberosum/genetics , Transcriptome , Apoptosis , Cyclopentanes/metabolism , Down-Regulation , Energy Metabolism , Ethylenes/metabolism , Gene Expression Regulation, Plant , Host-Pathogen Interactions , Oxylipins/metabolism , Photosynthesis , Plant Diseases/virology , Plant Growth Regulators/metabolism , Plant Immunity , Plant Leaves/genetics , Plant Leaves/immunology , Plant Leaves/virology , Plant Proteins/metabolism , Reactive Oxygen Species/metabolism , Signal Transduction , Solanum tuberosum/immunology , Solanum tuberosum/virologyABSTRACT
Hypersensitive resistance (HR) is an efficient defense strategy in plants that restricts pathogen growth and can be activated during host as well as non-host interactions. HR involves programmed cell death and manifests itself in tissue collapse at the site of pathogen attack. A novel hypersensitivity gene, Ny-1, for resistance to Potato virus Y (PVY) was revealed in potato cultivar Rywal. This is the first gene that confers HR in potato plants both to common and necrotic strains of PVY. The locus Ny-1 mapped on the short arm of potato chromosome IX, where various resistance genes are clustered in Solanaceous genomes. Expression of HR was temperature-dependent in cv. Rywal. Strains PVYO and PVYN, including subgroups PVYNW and PVYNTN, were effectively localized when plants were grown at 20 degrees C. At 28 degrees C, plants were systemically infected but no symptoms were observed. In field trials, PVY was restricted to the inoculated leaves and PVY-free tubers were produced. Therefore, the gene Ny-1 can be useful for potato breeding as an alternative donor of PVY resistance, because it is efficacious in practice-like resistance conferred by Ry genes.
Subject(s)
Genes, Plant/genetics , Immunity, Innate/genetics , Plant Diseases/virology , Potyvirus , Solanum tuberosum/genetics , Breeding/methods , Chromosome Mapping , DNA Primers/genetics , Reverse Transcriptase Polymerase Chain Reaction , Solanum tuberosum/virologyABSTRACT
Two new loci for resistance to potato virus M (PVM), Gm and Rm, have been mapped in potato. The gene Gm was derived from Solanum gourlayi, whereas, Solanum megistacrolobum is the source of the gene Rm. Gm confers resistance to PVM infection after mechanical inoculation. Rm induces a hypersensitive response in potato plants. Two diploid populations segregating for Gm and Rm, bulked segregant analysis (BSA) using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR), and available potato molecular maps were instrumental for mapping the resistance loci. The novel locus Gm was mapped to a central region on potato chromosome IX. The locus Rm was placed on the short arm of chromosome XI, close to the marker loci GP250 and GP283, where a hotspot for monogenic and polygenic resistance to diverse pathogens is located in the potato and tomato genome.
Subject(s)
Carlavirus/genetics , Chromosomes, Plant , Genes, Plant , Immunity, Innate/genetics , Solanum tuberosum/genetics , Carlavirus/immunology , Chromosome Mapping , DNA, Plant/analysis , DNA, Plant/genetics , DNA, Plant/isolation & purification , Diploidy , Genetic Markers , Microsatellite Repeats , Random Amplified Polymorphic DNA Technique , Sequence Analysis, DNA , Solanum tuberosum/virologyABSTRACT
A novel locus for potato resistance to potato leafroll virus (PLRV) was characterized by inheritance studies and molecular mapping. The diploid parental clone DW 91-1187 was resistant to PLRV accumulation in both inoculated plants and their tuber progeny. The resistance to PLRV accumulation present in DW 91-1187 was not transmitted to any F1 offspring when crossed with a PLRV susceptible clone. Instead, one half of the F1 individuals exhibited undetectable amounts of PLRV as determined by ELISA during the primary infection assay, but accumulated PLRV in their tuber progeny plants. The other half was clearly infected both in the inoculated and tuber-born plants. The inheritance of resistance to PLRV accumulation may be explained by a model of two complementary alleles of a single gene ( PLRV.4) or by two complementary genes that are closely linked in repulsion phase. Random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers linked to the PLRV.4 locus were selected. The two complementary factors were closely linked in coupling phase to the alternative alleles UBC864(600) and UBC864(800) of DNA marker UBC864. These markers may be used for marker-assisted selection of genotypes having both factors for resistance to PLRV accumulation. The PLRV.4 locus was mapped to a central position on linkage group XI of the potato molecular map, where no resistance locus has been mapped previously.
