Divergent molecular pathways govern temperature-dependent wheat stem rust resistance genes

Abstract

The wheat stem rust pathogen Puccinia graminis f. sp. tritici (Pgt) causes severe crop losses worldwide. Several stem rust resistance (Sr) genes exhibit temperature-dependent immune responses. Sr6-mediated resistance is enhanced at lower temperatures, whereas Sr13 and Sr21 resistances are enhanced at higher temperatures. Here, we clone Sr6 using mutagenesis and resistance gene enrichment and sequencing (MutRenSeq), identifying it to encode a nucleotide-binding leucine-rich repeat (NLR) protein with an integrated BED domain. Sr6 temperature sensitivity is also transferred to wheat plants transformed with the Sr6 gene. Differential gene expression analysis of near-isogenic lines inoculated with Pgt at varying temperatures reveals that genes upregulated in the low-temperature-effective Sr6 response differ from those upregulated in the high-temperature-effective responses associated with Sr13 and Sr21. These findings highlight divergent molecular pathways involved in temperature-sensitive immunity and inform future strategies for deployment and engineering of genetic resistance in response to a changing climate.