Rye Pm8 and wheat Pm3 are orthologous genes and show evolutionary conservation of resistance function against powdery mildew

Abstract

SUMMARYThe improvement of wheat through breeding has relied strongly on the use of genetic material from related wild and domesticated grass species. The 1RS chromosome arm from rye was introgressed into wheat and crossed into many wheat lines, as it improves yield and fungal disease resistance. Pm8 is a powdery mildew resistance gene on 1RS which, after widespread agricultural cultivation, is now widely overcome by adapted mildew races. Here we show by homology-based cloning and subsequent physical and genetic mapping that Pm8 is the rye orthologue of the Pm3 allelic series of mildew resistance genes in wheat. The cloned gene was functionally validated as Pm8 by transient, single-cell expression analysis and stable transformation. Sequence analysis revealed a complex mosaic of ancient haplotypes among Pm3-and Pm8-like genes from different members of the Triticeae. These results show that the two genes have evolved independently after the divergence of the species 7.5 million years ago and kept their function in mildew resistance. During this long time span the co-evolving pathogens have not overcome these genes, which is in strong contrast to the breakdown of Pm8 resistance since its introduction into commercial wheat 70 years ago. Sequence comparison revealed that evolutionary pressure acted on the same subdomains and sequence features of the two orthologous genes. This suggests that they recognize directly or indirectly the same pathogen effectors that have been conserved in the powdery mildews of wheat and rye.

The maize disease resistance gene Htn1 against northern corn leaf blight encodes a wall-associated receptor-like kinase

“…RT-qPCR primers and master mixes used for the targets ZmWAK-RLK1.1 and ZmWAK-RLK1.2 and the reference gene FPGS are described in SI Appendix, Table S8 (5 s for FPGS). Specificities of amplicons, RT-minus control check, and efficiency calculation were performed as described in Hurni et al (38). To allow comparison of the expression levels between the two splice variants ZmWAK-RLK1.1 and ZmWAK-RLK1.2, the RT-qPCR data were calibrated on the basis of plasmid DNA containing the ZmWAK-RLK1.1 or ZmWAK-RLK1.2 construct, respectively.…”

“…Expression of ZmWAK-RLK1 was quantified in a reverse transcription, quantitative real-time PCR (RT-qPCR) assay, using a CFX96 Real-Time System C1000TM Thermal cycler (Bio- (38), and first-strand cDNA was synthesized from 0.5 μg RNA, using 1/2 reaction of the iScript Advanced cDNA Kit (172-5038, Bio-Rad). RT-qPCR primers and master mixes used for the targets ZmWAK-RLK1.1 and ZmWAK-RLK1.2 and the reference gene FPGS are described in SI Appendix, Table S8 (5 s for FPGS).…”

Genomic Approaches Towards Durable Fungal Disease Resistance in Wheat

“…We have found that the Pm8 gene derived from rye and present on the frequently used 1RS/1BL translocation in wheat is an ortholog of the wheat Pm3 resistance gene (Hurni et al 2013 ). The fi nding that orthologous genes have maintained their function against the mildew pathogen over an estimated seven million years revealed a surprising evolutionary stability of powdery mildew resistance gene activity.…”

Molecular cloning, functional verification, and evolution of TmPm3, the powdery mildew resistance gene of Triticum monococcum L.

“…Nearly 70 Pm-resistance genes/alleles have been identified in wheat's germplasm, and many of them have been successfully used in breeding programs. However, only three of these genes have been cloned: Pm3, Pm8, and Pm21 (Yahiaoui et al, 2004;Cao et al, 2011;Hurni et al, 2013). Pm3 is located on the short arm of wheat's chromosome 1A and encodes a coiled-coil nucleotide-binding site leucine-rich repeat (CC-NBS-LRR)-resistance protein.…”

“…Pm3 is located on the short arm of wheat's chromosome 1A and encodes a coiled-coil nucleotide-binding site leucine-rich repeat (CC-NBS-LRR)-resistance protein. Pm8 was mapped to the short arm of rye's chromosome 1R, and cloned using a homology-based approach (Hurni et al, 2013).…”