Methods and compositions for modulating the sirna and rna-directed-dna methylation pathways

A method to identify a compound that enhances the expression or activity of a factor that modulates resistance of a plant or animal to infection by a pathogen, which method comprises either

• (a) modifying a plant or animal or cell to contain a nucleic acid construct that contains control sequences for the expression of a factor that enhances said resistance operatively linked to a nucleotide sequence that expresses a reporter;
• or
• (b) modifying a plant or animal or cell that constituitively expresses a reporter wherein said expression is downregulated by a resistance pathway to comprise an elicitor of said resistance pathway;
• and
• treating said plant, animal or cell with a candidate compound, and
• comparing the level of reporter expressed in the presence and absence of said compound wherein
• (i) higher expression of the reporter in the plant, animal or cell of (a);
• (ii) lower expression of the reporter in the plant, animal or cell of (a);
• (iii) lower expression of the reporter in the plant, animal or cell of (b);
• (iv) higher expression of the reporter in the plant, animal or cell of (b);
• identifies said compound as a compound that may enhance resistance to said pathogen.

A method to identify an endogenous factor that will enhance resistance to a pathogen which method comprises either

• (a) modifying a plant or animal or cell to contain a nucleic acid construct that contains control sequences for the expression of a factor that enhances said resistance operatively linked to a nucleotide sequence that expresses a reporter;
• or
• (b) modifying a plant or animal or cell that constituitively expresses a reporter wherein said expression is downregulated by a resistance pathway to comprise an elicitor of said resistance pathway;
• and
• mutagenizing said plant, animal or cell and identifying a plant, animal or cell wherein there is
• (i) higher expression of the reporter in the plant, animal or cell of (a);
• (ii) lower expression of the reporter in the plant, animal or cell of (a);
• (iii) lower expression of the reporter in the plant, animal or cell of (b);
• (iv) higher expression of the reporter in the plant, animal or cell of (b);
• and
• mapping the genome of the identified plant, animal or cell to identify mutated genes.