A giant NLR gene confers broad-spectrum resistance to Phytophthora sojae in soybean

Phytophthora root and stem rot caused by P. sojae is a destructive soybean soil-borne disease found worldwide. Discovery of genes conferring broad-spectrum resistance to the pathogen is a need to prevent the outbreak of the disease. Here, we show that soybean Rps11 is a 27.7-kb nucleotide-binding site-leucine-rich repeat (NBS-LRR or NLR) gene conferring broad-spectrum resistance to the pathogen. Rps11 is located in a genomic region harboring a cluster of large NLR genes of a single origin in soybean, and is derived from rounds of unequal recombination. Such events result in promoter fusion and LRR expansion that may contribute to the broad resistance spectrum. The NLR gene cluster exhibits drastic structural diversification among phylogenetically representative varieties, including gene copy number variation ranging from five to 23 copies, and absence of allelic copies of Rps11 in any of the non- Rps11 -donor varieties examined, exemplifying innovative evolution of NLR genes and NLR gene clusters. While multiple resistance-to- Phytophthora sojae loci/alleles have been mapped in soybean, many of them have become ineffective to newly evolved isolates. Here, the authors show that a 27.7-kb nucleotide-binding site-leucine-rich repeat gene confers broad-spectrum resistance to P. sojae in soybean.