Maize Rar1 polynucleotides and methods of use

Multicellular living organisms and unmodified parts thereof and – Method of introducing a polynucleotide molecule into or... – The polynucleotide confers pathogen or pest resistance

Reexamination Certificate

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C800S278000, C800S298000, C800S295000, C800S320000, C800S320100, C800S320200, C800S320300, C800S317000, C800S314000, C800S322000, C800S312000, C435S419000, C435S468000, C435S320100, C536S023600, C536S024100

Reexamination Certificate

active

06627796

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to plant molecular biology. More specifically, it relates to nucleic acids and methods for modulating their expression in plants and to transforming genes into plants in order to enhance disease resistance.
BACKGROUND OF THE INVENTION
Disease in plants is caused by biotic and abiotic causes. Biotic causes include fungi, viruses, insects, bacteria, and nematodes. Of these, fungi are the most frequent causative agents of disease in plants. Abiotic causes of disease in plants include extremes of temperature, water, oxygen, soil pH, plus nutrient-element deficiencies and imbalances, excess heavy metals, and air pollution.
A host of cellular processes enables plants to defend themselves from disease caused by pathogenic agents. These processes apparently form an integrated set of resistance mechanisms that is activated by initial infection and then limits further spread of the invading pathogenic microorganism.
Subsequent to recognition of a potentially pathogenic microbe, plants can activate an array of biochemical responses. Generally, the plant responds by inducing several local responses in the cells immediately surrounding the infection site. The most common resistance response observed in both nonhost and race-specific interactions is termed the “hypersensitive response” (HR). In the hypersensitive response, cells contacted by the pathogen, and often neighboring cells, rapidly collapse and dry in a necrotic fleck. Other responses include the deposition of callose, the physical thickening of cell walls by lignification, and the synthesis of various antibiotic small molecules and proteins. Genetic factors in both the host and the pathogen determine the specificity of these local responses, which can be very effective in limiting the spread of infection.
The hypersensitive response in many plant-pathogen interactions results from the expression of a resistance (R) gene in the plant and a corresponding avirulence (avr) gene in the pathogen. This interaction is associated with the hypersensitive response. R genes that respond to specific bacterial, fungal, or viral pathogens, have been isolated from a variety of plant species and several appear to encode cytoplasmic proteins.
The resistance gene in the plant and the avirulence gene in the pathogen often conform to a gene-for-gene relationship. That is, resistance to a pathogen is only observed when the pathogen carries a specific avirulence gene and the plant carries a corresponding or complementing resistance gene. Because avrR gene-for-gene relationships are observed in many plant-pathogen systems and are accompanied by a characteristic set of defense responses, a common molecular mechanism underlying avrR gene mediated resistance has been postulated. A simple model which has been proposed is that pathogen avr genes directly or indirectly generate a specific molecular signal that is recognized by cognate receptors encoded by plant R genes.
Both plant resistance genes and corresponding pathogen avirulence genes have been cloned. Race-specific single gene resistance controls powdery mildew, a common fungal pathogen. Such resistance is overcome when the pathogen evolves races that are not recognized by the resistance (R) gene in use in crops. In barley, the gene Rar1 is required for the powdery mildew resistance gene Mla12 to function. Barley Rar1 has been isolated (Shirasu, et al.,
Cell,
99:355-366 (1999)). Rar1 is also required for the function of some race-specific mildew resistance genes unrelated to Mla12.
Plant disease outbreaks have resulted in catastrophic crop failures that have triggered famines and caused major social change. Generally, the best strategy for plant disease control is to use resistant cultivars selected or developed by plant breeders for this purpose. However, the potential for serious crop disease epidemics persists today, as evidenced by outbreaks of the Victoria blight of oats and southern corn leaf blight. Accordingly, molecular methods are needed to supplement traditional breeding methods to protect plants from pathogen attack. The present invention provides maize Rar1 polynucleotides and polypeptides for manipulation of disease resistance in a plant.
SUMMARY OF THE INVENTION
Generally, it is the object of the present invention to provide nucleic acids and proteins relating to Rar1. It is an object of the present invention to provide transgenic plants comprising the nucleic acids of the present invention. It is another object of the present invention to provide methods for modulating, in a transgenic plant, the expression of the nucleic acids of the present invention.
Therefore, in one aspect, the present invention relates to an isolated nucleic acid comprising a member selected from the group consisting of (a) a polynucleotide encoding a polypeptide of the present invention; (b) a polynucleotide amplified from a
Zea mays
nucleic acid library using the primers of the present invention; (c) a polynucleotide comprising at least 20 contiguous bases of the polynucleotides of the present invention; (d) a polynucleotide encoding a maize Rar1 protein; (e) a polynucleotide having at least 90% sequence identity to the polynucleotides of the present invention; (f) a polynucleotide comprising at least 25 nucleotide in length which hybridizes under high stringency conditions to the polynucleotides of the present invention; and (g) a polynucleotide complementary to a polynucleotide of (a) through (f). The isolated nucleic acid can be DNA. The isolated nucleic acid can also be RNA.
In another aspect, the present invention relates to vectors comprising the polynucleotides of the present invention. Also the present invention relates to recombinant expression cassettes, comprising a nucleic acid of the present invention operably linked to a promoter.
In another aspect, the present invention is directed to a host cell into which has been introduced the recombinant expression cassette.
In yet another aspect, the present invention relates to a transgenic plant or plant cell comprising a recombinant expression cassette with a promoter operably linked to any of the isolated nucleic acids of the present invention. Preferred plants containing the recombinant expression cassette of the present invention include but are not limited to maize, soybean, sunflower, sorghum, canola, wheat, alfalfa, cotton, rice barley, and millet. The present invention also provides transgenic seed from the transgenic plant.
In another aspect, the present invention relates to an isolated protein selected from the group consisting of (a) a polypeptide comprising at least 40 contiguous amino acids of SEQ ID NO:2; (b) a polypeptide which is a maize Rar1 protein; (c) a polypeptide comprising at least 80% sequence identity to SEQ ID NO:2; (d) a polypeptide encoded by a nucleic acid of the present invention; and (e) a polypeptide characterized by SEQ ID NO:2.
In further aspect, the present invention relates to a method of modulating the level of protein in a plant by introducing into a plant cell a recombinant expression cassette comprising a polynucleotide of the present invention operably linked to a promoter; culturing the plant cell under plant growing conditions to produce a regenerated plant; and inducing expression of the polynucleotide for a time sufficient to modulate the protein of the present invention in the plant. Preferred plants of the present invention include but are not limited to maize, soybean, sunflower, sorghum, canola, wheat, alfalfa, cotton, rice, barley, and millet. The level of protein in the plant can either be increased or decreased.
DETAILED DESCRIPTION OF THE INVENTION
Overview
The present invention provides, among other things, compositions and methods for modulating (i.e., increasing or decreasing) the level of polynucleotides and polypeptides of the present invention in plants. In particular, the polynucleotides and polypeptides of the present invention can be expressed temporally or spatially, e.g., at developmental stages, in tissues, and/or in quantities, whi

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