A study by Wang et al., published in 2023, has furthered our understanding of wheat disease resistance by decoding the leaf rust resistance gene Lr9, initially derived from the wild grass species Aegilops umbellulata. Their research also revealed the emerging role of an unusual tandem kinase fusion protein encoded by this gene, broadening the available set of disease-resistance genes for breeding.
The researchers utilized mutagenesis and transcriptome sequencing to clone the Lr9 gene. This gene was first introduced into bread wheat from Ae. umbellulata as part of an established strategy to improve crop germplasm with disease-resistance genes by integrating chromosome segments from wild relatives.
They applied long-read sequencing to a wheat Lr9 introgression line and the putative Ae. umbellulata Lr9 donor, the team assembled the approximately 28.4-Mb Lr9 translocation and identified the translocation breakpoint.
Interestingly, the team also cloned another gene, Lr58, reportedly introduced from Aegilops triuncialis. Upon examination, it was found to have an identical coding sequence to Lr9. Cytogenetic and haplotype analyses further supported that both genes originated from the same translocation event.
The implications of these findings could be game-changing for the wheat farming industry. Wheat, a globally critical crop, is threatened by diseases such as leaf rust. By identifying and understanding the role of the Lr9 gene, breeders can enhance disease resistance in new wheat varieties.
This study also illuminates the significance of kinase fusion proteins in wheat disease resistance, offering a fresh perspective for future research. However, despite these promising results, the authors acknowledged that more research is needed to fully understand the potential of these proteins in protecting wheat and other crops against disease.