Structural Insights into AVR-Rmg8 Recognition Mechanisms by the Wheat Blast Resistance Gene Rmg8

Wheat blast disease, caused by the Triticum pathotype of Magnaporthe oryzae (MoT), poses a significant threat to global food security. The blast resistance gene Rmg8, recently isolated from a hexaploidy wheat cultivar, strongly confers resistance to all Bangladeshi and Zambian MoT isolates carrying the eI type of AVR-Rmg8. However, the molecular interactions underlying this recognition at proteins level remain poorly understood. In this study, we elucidated the structural and biological characteristics of RMG8 proteins and their recognition of the AVR-Rmg8 effector proteins using computational biology approaches. Amino acid sequence comparison of four AVR-Rmg8 types revealed that only three amino acid residues distinguish the eI type of AVR-Rmg8, which induces a higher level of resistance conferred by RMG8. We identified that the Protein Kinase C (PKC) domain of RMG8, where proline dependency mediates the phosphorylation of a serine residue, involves in the strong recognition of the eI type of AVR-Rmg8. Phylogenetic analyses indicated that Rmg8 might be evolved from proteins intimately linked to plant signaling pathways. Moreover, our data propose that RMG8 is a calcium-dependent multiple C2 domain proteins with transmembrane regions (MCTP) kinase that specifically recognizes the eI type of the AVR-Rmg8. Taken together, our in-silico predictions provide the first detailed insights into the molecular recognition mechanism between AVR-Rmg8 and RMG8, which is expected to aid in wheat blast resistance breeding. Future studies involving the purification and structural characterization of MoT effector proteins and Rmg8 gene products are necessary to validate these findings.