“Kinase fusion proteins in plant immunity”

   Annually crops face 40% loses due to insects, weeds and diseases. Among these, diseases play a significant role in causing economical loses to farmers. As a result, breeders engage in producing disease resistant varieties. Most part of plant breeder’s attention is towards disease resistance through major R-gene mediated resistance and among these R-genes, NBS-LRR (Nucleotide Binding Site and Leucine Rich Repeats) protein encoding genes have prominent role in resistance gene breeding. However, recent studies revealed another class of resistance genes encoding Kinase Fusion Proteins (KFPs) providing resistance for various diseases.

KFPs contain kinase domain fused with additional domain. KFPs arise through domain shuffling and domain duplication1. Additional domain in KFPs is involved in identification of pathogen by interacting with effectors and cause conformational change in kinase domain and as a consequence kinase domain functions in phosphorylation of proteins leading to signaling cascade to induce hypersensitive response and other resistance related responses. Complete structural and functional knowledge about KFP genes can assist in breeding resistant varieties through marker assisted selection, R-gene pyramiding, genome editing and bioinformatics tools1,2.

Fine mapping assists in identifying KFPs responsible for disease resistance in various crops. A fine mapping study was conducted in wheat and identified gene WTK3 that was a tandem kinase fusion protein having 6-bp deletion in resistant gene3. In another study, Un8 gene causing true loose smut in barely was fine mapped. Closely linked marker 0751D06 F6/R6 was identified to use in marker assisted selection and gene responsible for resistance was identified as tandem kinase domain protein4. Together these studies highlight importance of KFP genes in resistance breeding.

In conclusion, KFPs are emerging proteins that have a significant role in disease resistance as number of fine mapped genes for disease resistance is occurring to be KFPs. So, there is a need to focus more on these KFPs especially towards bioinformatics and molecular field to develop additional cloning and gene annotation methods for these KFPs so that breeders can produce disease resistance varieties and lower the loses occurring due to diseases in crop plants.

References

 1LIU, Y., HOU, S. AND CHEN, S., 2023, Kinase fusion proteins: intracellular R-proteins in plant immunity. Trends Plant Sci., 10.1016/j.tplants.2023.11.002. 

2KLYMIUK, V., COAKER, G., FAHIMA, T. AND POZNIAK, C. J., 2021, Tandem protein kinases emerge as new regulators of plant immunity. Mol. Plant Microbe Interact, 34 (10) : 1094 - 1102. 

3LU, P., GUO, L., WANG, Z., LI, B., LI, J., LI, Y., QIU, D., SHI, W., YANG, L., WANG, N. AND GUO, G., 2020, A rare gain of function mutation in a wheat tandem kinase confers resistance to powdery mildew. Nat. comm., 11 (1) : 680.

 4ZANG, W., ECKSTEIN, P.E., COLIN, M., VOTH, D., HIMMELBACH, A., BEIER, S., STEIN, N., SCOLES, G.J. AND BEATTIE, A.D., 2015, Fine mapping and identification of a candidate gene for the barley Un8 true loose smut resistance gene. Theor. Appl. Genet., 128 : 1343 - 1357.