Abstract
Tomato yellow leaf curl virus (TYLCV) is a devastating disease of tomato (Solanum lycopersicum) that can be effectively controlled by the deployment of resistant cultivars. The TYLCV-resistant line TY172 carries a major recessive locus for TYLCV resistance, designated ty-5, on chromosome 4. In this study, the association between 27 polymorphic DNA markers, spanning the ty-5 locus, and the resistance characteristics of individual plants inoculated with TYLCV in 51 segregating recombinant populations were analyzed. These analyses localized ty-5 into a 425 bp region containing two transversions: one in the first exon of a gene encoding the tomato homolog of the messenger RNA surveillance factor Pelota (Pelo), and a second in its proximal promoter. Analyses of susceptible and resistant lines revealed that the relative transcript level of the gene remained unchanged, regardless of whether the plants were infected with TYLCV or not. This suggests that the polymorphism discovered in the coding region of the gene controls the resistance. Silencing of Pelo in a susceptible line rendered the transgenic plants highly resistant, while in the resistant line TY172 had no effect on symptom development. In addition, over-expression of the susceptible allele of the gene in the resistant TY172 line rendered it susceptible, while over-expression of the resistant allele in susceptible plants had no effect. These results confirm that Pelo is the gene controlling resistance at the ty-5 locus. Pelo, implicated in the ribosome recycling-phase of protein synthesis, offers an alternative route to promote resistance to TYLCV and other viruses.
Highlights
Tomato yellow leaf curl virus (TYLCV) is one of the most devastating viruses of cultivated tomatoes, Solanum (S.) lycopersicum
To fine-tune map the introgression in the TYLCV-resistant line TY172, carrying the ty-5 gene, we have sequenced 800-to-900 bp fragments of its genome spanning the NAC DOMAIN 1 protein (Nac1) gene region (first, approximately every 50 Kilo bp (Kbp), every 10 Kbp and every 3 Kbp and at times even in smaller intervals)
These sequencing results were compared to the sequence of the reference genome Heinz 1706, known to be susceptible to TYLCV in order to identify nucleotide polymorphisms
Summary
Tomato yellow leaf curl virus (TYLCV) is one of the most devastating viruses of cultivated tomatoes, Solanum (S.) lycopersicum. TYLCV induces severe cupping of apical leaves, yellowing, and stunting, resulting in considerable yield losses. TYLCV has become a major limiting factor to tomato production in major tomato-growing areas, including: China, Mexico, Florida and California [4, 5]. TYLCV is a monopartite begomovirus (family Geminiviridae) transmitted by the whitefly Bemisia tabaci (Gennadius). Population outbreaks of whiteflies are often associated with a high incidence of the disease [6]. Management of TYLCV is difficult because its whitefly vector populations can reach enormous numbers. Breeding TYLCV-resistant tomato cultivars provides an attractive, environmentally sound, strategy to reduce yield losses inflicted by the virus [4, 7,8,9]
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