Use of an Autoimmune Mutant to Probe the Maize Defense Response

The hypersensitive response (HR) is a defense response found in all higher plants in which resistance (R-) proteins in the first infected cells detect the presence of specific molecules associated with the pathogen and initiate a series of defense responses including rapid cell death.  In many cases this halts the infection before it can spread to other cells in the plant.  Despite its importance in maintaining healthy crops, much remains unknown about the HR.  We have used a novel genetic screen involving Rp1-D21, an autoactive R-protein from maize that confers a constitutive HR, to identify loci, genes and pathways associated with natural genetic variation controlling HR in maize.   We have shown that proteins encoded by some these of these genes interact specifically with the Rp1-D21 protein to inhibit the HR.  Other genes appear to act in a more general way to suppress programed cell death.