A kinase fusion protein from Aegilops longissima confers resistance to wheat powdery mildew

A substantial number of disease resistance genes have been introgressed into bread wheat from wild wheat relatives in the past decades. However, reduced recombination within the introgressed segments greatly hinders the cloning of introgressed genes. Here, by combining physical mapping through radiation-induced chromosomal aberrations and transcriptome sequencing of six ethyl methanesulfonate (EMS)-induced loss-of-function mutants, we cloned the broad-spectrum powdery mildew resistance gene Pm13 that was introgressed into bread wheat from Aegilops longissima. Pm13 encodes a kinase fusion protein with an N-terminal domain of mixed lineage kinase domain-like protein (MLKL_NTD domain) and a C-terminal serine/threonine kinase domain bridged by a brace, designated MLKL-K. The resistance function of Pm13 was validated by transient and stable transgenic complementation assays. Transient over-expression analysis in Nicotiana benthamiana leaves revealed that the fragment Brace-Kinase122-476 of MLKL-K is capable of inducing cell death, which is dependent on kinase activity and the alpha-helices in the brace region. The identification and characterization of Pm13 will facilitate powdery mildew resistance breeding and uncovering molecular mechanism of emerging kinase fusion proteins.