Multicellular living organisms and unmodified parts thereof and – Plant – seedling – plant seed – or plant part – per se – Higher plant – seedling – plant seed – or plant part
Reexamination Certificate
2001-03-09
2003-12-16
Mehta, Ashwin (Department: 1638)
Multicellular living organisms and unmodified parts thereof and
Plant, seedling, plant seed, or plant part, per se
Higher plant, seedling, plant seed, or plant part
C435S320100, C435S419000, C435S468000, C435S471000, C536S023600, C800S279000, C800S298000, C800S317400
Reexamination Certificate
active
06664447
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a plant nucleic acid which confers resistance to plants to Tospoviruses, and uses thereof.
BACKGROUND OF THE INVENTION
Tospoviruses are thrips-transmitted viruses that belong to the genus Tospovirus (family Bunyaviridae) and cause substantial yield loss to ornamental and vegetable crops in several areas of the world (German et al., “Tospoviruses: Diagnosis, Molecular Biology, Phylogeny, and Vector Relationships,”
Annu. Rev. of Phytopathol
30:315-348 (1992); Peters et al., “Vector Relations in the Transmission and Epidemiology of Tospoviruses. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:29-42 (1996)). The members of this genus are characterized by a genome comprised of three separate single stranded RNAs (S, M, and L RNAs) enveloped in a lipidic membrane and associated with two glycoproteins, G1 and G2 (German et al., “Tospoviruses: Diagnosis, Molecular Biology, Phylogeny, and Vector Relationships,”
Annu. Rev. of Phytopathol
30:315-348 (1992); van Poelwijk et al., “Replication and Expression of the Tospovirus Genome. Proceedings of the International Symposium on Tospovirus and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:201-208 (1996)). Based on serological properties, vector specificity, host range, and nucleotide and amino acid sequences of the nucleoprotein gene, several species have been established in the genus Tospovirus (de Ávila et al., “Classification of Tospoviruses Based on Phylogeny of Nucleoprotein Gene Sequences,”
J. Gen. Virol
74:153-159 (1993); Goldbach et al., “Introduction. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:21-26 (1996); Peters et al., “Vector Relations in the Transmission and Epidemiology of Tospoviruses. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:29-42 (1996)). Tomato spotted wilt virus (TSWV), tomato chlorotic spot virus (TCSV), impatiens necrotic spot virus (INSV), and groundnut ringspot virus (GRSV) are the Tospovirus species commonly associated with important yield losses in the tomato crop. TSWV, the type species of the genus, has a worldwide distribution, whereas GRSV and TCSV have, thus far, only been identified on tomatoes grown in Brazil and Argentina (Dewey et al., “Molecular Diversity of Tospovirus in Argentina: A Summary. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:261-263 (1996); Peters et al., “Vector Relations in the Transmission and Epidemiology of Tospoviruses. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:29-42 (1996); Resende et al., “New Tospovirus Species Found in Brazil. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:78-89 (1996)). In Brazil, new tospovirus species that infect tomato are also being characterized (Resende et al., “New Tospovirus Species Found in Brazil. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:78-89 (1996)).
Because genetic resistance offers the best means of protecting crop plants against tospovirus infection, considerable effort has been devoted to the development of resistant varieties (Cho et al., “Conventional Breeding: Host-Plant Resistance and the Use of Molecular Markers to Develop Resistance to Tomato Spotted Wilt Virus in Vegetables. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:367-378 (1996); Roselló et al., “Genetics of Tomato Spotted Wilt Virus Resistance Coming From
Lycopersicon peruvianum,” Eur. J. of Plant Path.
104:499-509 (1998)). Naturally occurring host resistance to tospoviruses has been reported in many Lycopersicon species (Finlay, “Inheritance of Spotted Wilt Resistance in Tomato. II. Five Genes Controlling Spotted Wilt Resistance in Four Tomato Types,”
Aust. J. Biol. Sci.
6:153-163 (1953); Cho et al., “Conventional Breeding: Host-Plant Resistance and the Use of Molecular Markers to Develop Resistance to Tomato Spotted Wilt Virus in Vegetables. In: International Symposium on Tospoviruses and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:367-378 (1996); Krishna Kumar et al., “Evaluation of Lycopersicum Germplasm for Tomato Spotted Wilt Tospovirus Resistance by Mechanical and Thrips Transmission,”
Plant Dis.
77:938-941 (1993); Paterson et al., “Resistance in Two Lycopersicon Species to an Arkansas Isolate of Tomato Spotted Wilt Virus,”
Euphytica
43:173-178 (1989); Roselló et al., “Viral Diseases Causing the Greatest Economic Losses to the Tomato Crop. I. The Tomato Spotted Wilt Virus—A Review,”
Scientia Horticulturae
67:117-150 (1996); Stevens et al., “Evaluation of Seven Lycopersicon Species for Resistance to Tomato Spotted Wilt Virus (TSWV),”
Euphytica
80:79-84 (1994)). However, in many cases, this resistance is species and/or isolate specific and therefore not very useful for breeding purposes. Broad spectrum tospovirus resistance was found in the
L. esculentum
cultivar ‘Stevens’ (van Zijl et al., “Breeding Tomatoes for Processing in South Africa,”
Acta Horticulturae
194:69-75 (1986)). The TSWV resistance of this cultivar, introgressed from an unknown
L. peruvianum
accession, is conferred by a single gene, Sw-5, which is incompletely dominant (Stevens et al., “Inheritance of a Gene for Resistance to Tomato Spotted Wilt Virus (TSWV) From
Lycopersicon peruvianum
Mill,”
Euphytica
59:9-17 (1992)). This gene also seems to provide resistance to TCSV and GRSV (Boiteux et al., “Genetic Basis of Resistance Against Two Tospovirus Species in Tomato (
Lycopersicon esculentum
),”
Euphytica
71:151-154 (1993)).
Genes conferring resistance to different isolates of the same pathogen or different pathogens are often organized in the plant genome as tandem arrays of homologues (Hammond-Kosack et al., “Plant Disease Resistance Genes,”
Annu. Rev. Plant Physiol. Plant Mol. Biol.
48:575-607 (1997)). Therefore, the multiple resistances conferred by Sw-5 raise the question of whether the Sw-5 locus consists of a cluster of tightly linked genes, each gene having its own virus specificity, or whether it encodes a single gene product capable of recognizing several tospovirus isolates and species. In addition, the physiological mechanism by which Sw-5 provides resistance is unclear. In tomato plants carrying Sw-5, the virus cannot spread systemically throughout the plant; and, in many cases, the inoculated leaves do not show any macroscopic symptoms. However, for some tospovirus isolates and/or under high inoculum pressure, local and systemic necrotic lesions appear on the inoculated plants, suggesting that Sw-5 resistance can elicit a hypersensitive response (Stevens et al., “Inheritance of a Gene for Resistance to Tomato Spotted Wilt Virus (TSWV) From
Lycopersicon peruvianum
Mill,”
Euphytica
59:9-17 (1992); Brommonschenkel et al., “Map-based Cloning of the Tomato Genomic Region that Spans the Sw-5 Tospovirus Resistance Gene in Tomato,”
Mol. Gen. Genet.
256:121-126 (1997); Roselló et al., “Genetics of Tomato Spotted Wilt Virus Resistance Coming From
Lycopersicon peruvianum,” Eur. J. of Plant Path.
104:499-509 (1998)). Sw-5 may also be developmentally regulated, as the resistance gene does not appear to provide tospovirus resistance in tomato fruits (de Haan et al., “Transgenic Tomato Hybrids Resistant to Tomato Spotted Wilt Virus Infection. In: International Symposium on Tospoviruses, and Thrips of Floral and Vegetable Crops,”
Acta Horticulturae
431:417-426 (1996)).
These unusual characteristics of Sw-5 and its tight linkage to RFLP marker CT220 on the long arm of tomato chromosome 9 led to the isolation of this gene via map-based cloning. By high resolution-genetic linkage analysis of Sw-5 recombinant plants and chromosome walking, it was demonstr
Brommonschenkel Sergio H.
Tanksley Steven D.
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