Stem rust resistance in wheat is suppressed by a subunit of the mediator complex

Hiebert, C.W., Moscou, M.J., Hewitt, T., Steuernagel, B., Hernández-Pinzón, I., Green, P., Pujol, V., Zhang, P., Rouse, M.N., Jin, Y., McIntosh, R.A., Upadhyaya, N., Zhang, J., Bhavani, S., Vrána, J., Karafiátová, M., Huang, L., Fetch, T., Doležel, J., Wulff, B.B.H., Lagudah, E., Spielmeyer, W.

Abstract: Stem rust is an important disease of wheat that can be controlled using resistance genes. The gene SuSr-D1 identified in cultivar 'Canthatch' suppresses stem rust resistance. SuSr-D1 mutants are resistant to several races of stem rust that are virulent on wild-type plants. Here we identify SuSr-D1 by sequencing flow-sorted chromosomes, mutagenesis, and map-based cloning. The gene encodes Med15, a subunit of the Mediator Complex, a conserved protein complex in eukaryotes that regulates expression of protein-coding genes. Nonsense mutations in Med15b.D result in expression of stem rust resistance. Time-course RNAseq analysis show a significant reduction or complete loss of differential gene expression at 24 h post inoculation in med15b.D mutants, suggesting that transcriptional reprogramming at this time point is not required for immunity to stem rust. Suppression is a common phenomenon and this study provides novel insight into suppression of rust resistance in wheat.
DOI: 10.1038/s41467-020-14937-2
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IEB authors: Jaroslav Doležel, Miroslava Karafiá..., Jan Vrána