Adjusting defense response strength level using the Cf-Ecp5 gene as a model.

Four Cf-Ecp5 loci are located on three chromosomes, showing differences in HR strength in both PVX:Ecp5 assays and crosses to Ecp5-expressing plants.Allelism crosses revealed suppression of HR in some F1 and most F2 crossing combinations, suggesting distinct evolution of effector recognition or defense signaling.Notably, suppression or enhancement in some cases (G1.1161 x LA0722) occurred in crosses between accessions carrying Cf-Ecp5 genes at the same or different locus, but the suppressive elements were unlinked to that locus and appeared accessionspecific.Also, there was observable segregation of differences in strength response, qualitative and quantitative in nature.Preliminary analysis by whole genome sequencing suggests that Cf-Ecp5 loci encode RLPs that likely depend on RLKs like SOBIR1 or BAK1 for immune signaling.Exception is the LA0722, which appears to encode an RLK.Whether all Cf-Ecp5 proteins require the same or similar co-receptors remains unclear.However, the observed HR suppression/enhancement across crosses can provide clear insights into differences in their signaling mechanisms.These differences can be exploited to adjust the strength level of response and counteract any detrimental effect of fitness cost associated with it.