Development of a locus-specific, co-dominant SCAR marker for assisted-selection of the Sw-5 (Tospovirus resistance) gene cluster in a wide range of tomato accessions

The best levels of broad-spectrum Tospovirus resistance reported in tomatoes thus far are conferred by the Sw-5 locus. This locus contains at least five paralogues (denoted Sw-5a through Sw-5e), of which Sw-5b represents the actual resistance gene. Here we evaluated a panel of seven PCR primer pairs matching different sequences within a genomic region spanning the Sw-5a and Sw-5b gene cluster. Primer efficiency evaluation was done employing tomato isolines with and without the Sw-5 locus. One primer pair produced a single and co-dominant polymorphism between susceptible and resistant isolines. Sequence analysis of these amplicons indicated that they were specific for the Sw-5 locus and their differences were due to insertions/deletions. The polymorphic SCAR amplicon encompass a conserved sequence of the promoter region of the functional Sw-5b gene, being located in the position -31 from its open reading frame. This primer pair was also evaluated in field assays and with a collection of accessions known to be either susceptible or resistant to tospoviruses. An almost complete correlation was found between resistance under greenhouse/field conditions and the presence of the marker. Therefore, this primer pair is a very useful tool in marker-assisted selection systems in a large range of tomato accessions

The Tomato spotted wilt virus cell-to-cell movement protein (NSM) triggers a hypersensitive response in Sw-5 containing resistant tomato lines and Nicotiana benthamiana transformed with the functional Sw-5b resistance gene copy.

Although the Sw-5 gene cluster has been cloned, and Sw-5b has been identified as the functional gene copy that confers resistance to Tomato spotted wilt virus (TSWV), its avirulence (Avr) determinant has not been identified to date. Nicotiana tabacum SR1 plants transformed with a copy of the Sw-5b gene are immune without producing a clear visual response on challenge with TSWV, whereas it is shown here that N.benthamiana transformed with Sw-5b gives a rapid and conspicuous hypersensitive response (HR). Using these plants, from all structural and non-structural TSWV proteins tested, the TSWV cell-to-cell movement protein (NSM) was confirmed as the Avr determinant using a Potato virus X (PVX) replicon or a non-replicative pEAQ-HT expression vector system. HR was induced in Sw-5b-transgenic N.benthamiana as well as in resistant near-isogenic tomato lines after agroinfiltration with a functional cell-to-cell movement protein (NSM) from a resistance-inducing (RI) TSWV strain (BR-01), but not with NSM from a Sw-5 resistance-breaking (RB) strain (GRAU). This is the first biological demonstration that Sw-5-mediated resistance is triggered by the TSWV NSM cell-to-cell movement protein

Preserving accuracy in GenBank

GenBank, the public repository for nucleotide and protein sequences, is a critical resource for molecular biology, evolutionary biology, and ecology. While some attention has been drawn to sequence errors, common annotation errors also reduce the value of this database. In fact, for organisms such as fungi, which are notoriously difficult to identify, up to 20% of DNA sequence records may have erroneous lineage designations in GenBank. Gene function annotation in protein sequence databases is similarly error-prone. Because identity and function of new sequences are often determined by bioinformatic analyses, both types of errors are propagated into new accessions, leading to long-term degradation of the quality of the database. Currently, primary sequence data are annotated by the authors of those data, and can only be reannotated by the same authors. This is inefficient and unsustainable over the long term as authors eventually leave the field. Although it is possible to link third-party databases to GenBank records, this is a short-term solution that has little guarantee of permanence. Similarly, the current third-party annotation option in GenBank (TPA) complicates rather than solves the problem by creating an identical record with a new annotation, while leaving the original record unflagged and unlinked to the new record. Since the origin of public zoological and botanical specimen collections, an open system of cumulative annotation has evolved, whereby the original name is retained, but additional opinion is directly appended and used for filing and retrieval. This was needed as new specimens and analyses allowed for reevaluation of older specimens and the original depositors became unavailable. The time has come for the public sequence database to incorporate a community-curated, cumulative annotation process that allows third parties to improve the annotations of sequences when warranted by published peer-reviewed analyses.Fil: Bidartondo, Martin I.. Imperial College London; Reino Unido. Royal Botanic Gardens; Reino UnidoFil: Bruns, Thomas D.. University of California at Berkeley; Estados UnidosFil: Blackwell, Meredith. Louisiana State University; Estados UnidosFil: Edwards, Ivan. University of Michigan; Estados UnidosFil: Taylor, Andy F. S.. Swedish University of Agricultural Sciences; SueciaFil: Bianchinotti, Maria Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur; ArgentinaFil: Padamsee, Mahajabeen. University of Minnesota; Estados UnidosFil: Callac, Philippe. Institut National de la Recherche Agronomique; FranciaFil: Lima, Nelson. Universidade do Minho; PortugalFil: White, Merlin M.. Boise State University; Estados UnidosFil: Barreau Daly, Camila. Centre National de la Recherche Scientifique; Francia. Institut National de la Recherche Agronomique; FranciaFil: Juncai, M. A.. Chinese Academy of Sciences; República de ChinaFil: Buyck, Bart. Museum National d'Histoire Naturelle; FranciaFil: Rabeler, Richard K.. University of Michigan; Estados UnidosFil: Liles, Mark R.. Auburn University; Estados UnidosFil: Estes, Dwayne. Austin Peay State University; Estados UnidosFil: Carter, Richard. Valdosta State University; Estados UnidosFil: Herr Jr., J. M.. University of South Carolina; Estados UnidosFil: Chandler, Gregory. University of North Carolina; Estados UnidosFil: Kerekes, Jennifer. University of California at Berkeley; Estados UnidosFil: Cruse Sanders, Jennifer. Salem College Herbarium; Estados UnidosFil: Galán Marquez, R.. Universidad de Alcalá; EspañaFil: Horak, Egon. Zurich Herbarium; SuizaFil: Fitzsimons, Michael. University of Chicago; Estados UnidosFil: Döering, Heidi. Royal Botanic Gardens; Reino UnidoFil: Yao, Su. China Center of Industrial Culture Collection; ChinaFil: Hynson, Nicole. University of California at Berkeley; Estados UnidosFil: Ryberg, Martin. University Goteborg; SueciaFil: Arnold, A. E.. University of Arizona; Estados UnidosFil: Hughes, Karen. University of Tennessee; Estados Unido