| Age-Related Resistance (ARR) has been observed in numerous plant species, resulting in increased disease resistance as the plant matures. The ARR defective mutant, iap1-1, (i&barbelow;mportant in the A&barbelow;RR p&barbelow;athway,) was discovered in an ARR mutant screen and EDS1, (e&barbelow;nhanced d&barbelow;isease s&barbelow;usceptibility,) which is involved in other disease resistance pathways, was shown to be required for ARR. Intercellular accumulation of salicylic acid (SA) is required for ARR suggesting that SA may act as an anti-microbial agent. Mature (6 wpg) iap1-1 does not accumulate intercellular or intracellular SA in response to Pst inoculation. Intercellular and intracellular SA accumulation is also partially reduced in young (4 wpg) plants during R gene-mediated resistance to Pst(AvrRpt2) which is partially compromised suggesting that the two pathways share common elements. The novel discovery of the presence of intercellular SA during R gene-mediated resistance suggests that it may act as an antimicrobial agent during R gene-mediated resistance as it is hypothesized to during ARR. The iap1-1 mutation maps to chromosome four between 17,938,268bp and 18,133,423b. The semi-dominant, loss of function nature of the iap1-1 mutation suggests that IAP1 is a positive regulator in the ARR pathway. |
