Email: Rajagopal.subramaniam@agr.gc.ca

Fusarium graminearum is a pathogen of small grain cereal crops such as wheat, maize, and barley. As functional genomics resources in cereals continue to improve, Arabidopsis remains an attractive non-host model for plant-microbe interaction studies. Resistance to F. graminearum (Fg) does not follow the classic gene for gene interaction; therefore, atypical resistance components must be involved. Previously, a reverse genetics screen in Arabidopsis identified several pattern recognition receptors (PRRs) with a role in F. graminearum resistance.

Two of the genes identified in our screen, APEX, and the danger-associated molecular patterns (DAMP) receptor RLK7 as negative regulators of defense against Fg infection. Accordingly, the double mutant rllk7/apex displayed enhanced resistance to Fg and therefore, was used as a screening platform to functionally characterize RLK7 and Apex alleles from wheat.

The results clarified the role of Apex as the negative regulator, whereas RLK7 is one of the several PRRs that are activated after infection in Arabidopsis. The family of PBL cytoplasmic receptor kinases are the immediate downstream targets of fungal PRRs, such as CERK1. We were also interested in the role of these kinases in Fg resistance.

A combination of genetic and chemical studies directly implicated PBL27 and its corresponding resistance gene Zar1 in Fg resistance. Together, these studies suggest a role for both membrane and cytoplasmic receptor kinases in the resistance to Fg that holds a prospect of pyramiding resistance genes to improve resistance against FHB in wheat.