Positional cloning of the wheat stripe rust resistance gene Yr15 have led to the discovery of the tandem kinase-pseudokinase (TKP) protein family

Wheat production, as one of the most important food crops for human consumption globally, is affected by different biotic (diseases) and abiotic (natural growth conditions) stresses. Yr15 is a wild emmer wheat (Triticum dicoccoides) broad-spectrum stripe rust disease resistance gene. Comparative genomics, chromosome walking, BAC libraries (wild emmer and bread wheat), whole genome assemblies, EMS mutagenesis and transgenic approaches enabled us to clone Yr15 and validate its function. Analysis of the protein encoded by Yr15 revealed that it has a putative kinase-pseudokinase structure, designated as Wheat Tandem Kinase 1 (WTK1). WTK1 orthologs and paralogs are found in all group 1 and 6 wheat chromosomes of the available reference wheat genomes Chinese Spring, Svevo and Zavitan. The unique protein domain architecture of WTK1 was found in 92 putative proteins across the plant kingdom, including the barley RPG1 and a candidate for Un8, suggesting that they are members of a distinct family of plant proteins, termed here tandem kinase-pseudokinases (TKPs). We found that 175 out of 184 kinase/pseudokinase domains of these TKPs were associated with receptor-like kinases (RLKs), suggesting that TKPs are involved in plant defense mechanisms. Further phylogenetic analysis indicated that TKP family members originated from either gene duplication or gene fusion events, suggesting a polyphyletic origin of the TKPs. The decoy role can be proposed as one of the potential model of function of the pseudokinases of TKP family members in immune response.