Poster: Plant-pathogen interactions

Abs # 520: Characterization and cloning of mos4, a suppressor of constitutive disease resistance in snc1

Presenter:	Palma, Kristoffer , palma@interchange.ubc.ca
Authors	Palma, Kristoffer  (A)   Zhang, Yuelin  (A)   Li, Xin  (A)
Affiliations:	(A): University Of British Columbia

Plants are under constant threat of infection by pathogens aiming to colonize their host. As a result, they have evolved sophisticated response systems against pathogen infection. Initiation of defense signaling often involves specific recognition of invading pathogens by the products of specialized host resistance (R) genes. Genetic analysis of mutants impaired in mounting a resistance response to invading pathogens has uncovered a number of distinct, but interconnecting, signaling networks of which R-genes play a central role. In Arabidopsis, a dominant mutant, snc1, was previously identified that constitutively expresses pathogenesis-related (PR) genes and disease resistance against both Pseudomonas syringae maculicola (Psm) ES4326 and Peronospora parasitica Noco2 in the npr1-1 background. SNC1 encodes an RPP5 homolog – a single amino acid change in the region between the NB-ARC and LRR of SNC1 renders this R-protein constitutively active. Outside of the npr1-1 background, snc1 plants exhibit a similar resistance phenotype, have high levels of endogenous salicylic acid (SA), and are stunted and have curly leaves. To identify genes important for signaling in snc1, we carried out a genetic screen to identify mos (modifier of snc1) mutants that affect PR gene expression in snc1 plants. One such mutant, mos4, was isolated and mapped to a small region on chromosome 3. In mos4, constitutive PR gene expression, elevated SA, and pathogen resistance have been abolished, and the morphology is reverted to wild type. A putative mutation has been identified in mos4. The characterization, cloning, and significance of MOS4 will be discussed.