Chemistry: molecular biology and microbiology – Plant cell or cell line – per se ; composition thereof;... – Plant cell or cell line – per se – is pest or herbicide...
Patent
1995-12-01
1999-07-06
Stucker, Jeffrey
Chemistry: molecular biology and microbiology
Plant cell or cell line, per se ; composition thereof;...
Plant cell or cell line, per se, is pest or herbicide...
435 691, 435 697, 435419, 536 231, 536 2372, 536 241, 800278, 800279, 800288, 800301, A01H 400, C12N 514, C07H 2100
Patent
active
059197056
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The present invention relates to pathogen resistant plants and in particular to pathogen resistant plants wherein pathogen resistance is triggered in response to invading pathogens such as viruses, DNA constructs for use in such plants and methods of introducing virus induced resistance into plants.
Viral infections in plants are frequently responsible for detrimental effects in growth, undesirable morphological changes, decreased yield and the like. Such infections often result in a higher susceptibility to infection in infected plants to other plant pathogens and plant pests.
Virus particles generally comprise a relatively small amount of genetic material (single or double stranded RNA or DNA) protected by a protein or proteins which in some viral types can also be surrounded with host-derived lipid membranes, yielding infectious particles. Viruses are dependent on host cells for multiplication and may therefore be regarded as intracellular parasites.
Plants have evolved a number of defensive mechanisms to limit the effects of viral infection. For example, so-called horizontal or partial resistances which are polygenic in nature and so-called vertical resistances which are monogenic in nature.
Horizontal resistance is difficult to introduce successfully into plants in breeding programs, however, vertical resistance can be bred into plants relatively easily within plant breeding programs. Genes coding for virus resistance can act constitutively in a passive sense, ie without a requirement for inducing gene expression. Constitutively expressed virus resistances include as modes of action non-host resistances, tolerance ie inhibition of disease establishment, immunity ie inhibition of transport or the presence of antiviral agents and the like. Alternatively, genes coding for virus resistance in plants can be actively switched on by way of inducing expression of a gene or genes encoding for a viral resistance. An example of such a system includes the hypersensitive response.
So-called hypersensitive responses (HSR) in plants have been reported and are generally characterized by death of plant cells in the vicinity of the penetrating pathogen shortly after infection. Movement of the pathogen through infected or invaded cells is restricted or blocked due to necrosis of the invaded cell and/or cells in the environs of the invaded cell(s). In addition, HSR involves a cascade of additional or secondary defense responses and the accumulation of certain proteins and secondary metabolites, leading to a general increased level of resistance to attack by pathogens. HSR reactions to invading organisms are generally thought to involve a resistance gene product in the plant cell which recognizes and interacts with an elicitor element, ie the product of an avirulence gene of a pathogen. Elicitor element recognition in the cells of a resistant plant triggers an HSR reaction which in its turn restricts the pathogen infection to a single cell or cells, or at most to a few plant cells in the immediate vicinity thereof.
An example of HSR-mediated resistance to virus infection is that of tobacco plants harbouring the N' resistance gene to tobamoviruses such as TMV and ToMV, which contain the coat protein avirulence gene. Thus far, more than twenty single dominant HSR-type resistance genes have been identified, and are present in many agronomically important crops including tobacco, tomato, potato, pepper, lettuce, and the like.
Despite the apparent abundance of resistance sources to certain viruses, many crops still lack effective resistance genes to important viral type germplasm collections has identified only a few suitable sources of viral resistance capable of being introduced successfully into agronomically important crops. An example is the absence of vertical resistance genes to cucumber mosaic virus (CMV) in many agronomically important crop types including but not limited to tomato, pepper, cucumber, melon, lettuce and the like.
Plant breeders continuously try to develop varieties of crop plant species tol
REFERENCES:
patent: 5614395 (1997-03-01), Ryals et al.
Nejidat et al. Physiologia Plantarium, vol. 80 pp. 662-668, 1990.
Bui Phuong T.
Hoxie Thomas
Meigs J. Timothy
Novartis Finance Corporation
Stucker Jeffrey
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