The receptor like kinase at Rhg1-a/Rfs2 caused pleiotropic resistance to sudden death syndrome and soybean cyst nematode as a transgene by altering signaling responses

Abstract

BackgroundSoybean (Glycine max (L. Merr.)) resistance to any population of Heterodera glycines (I.), or Fusarium virguliforme (Akoi, O’Donnell, Homma & Lattanzi) required a functional allele at Rhg1/Rfs2. H. glycines, the soybean cyst nematode (SCN) was an ancient, endemic, pest of soybean whereas F. virguliforme causal agent of sudden death syndrome (SDS), was a recent, regional, pest. This study examined the role of a receptor like kinase (RLK) GmRLK18-1 (gene model Glyma_18_02680 at 1,071 kbp on chromosome 18 of the genome sequence) within the Rhg1/Rfs2 locus in causing resistance to SCN and SDS.ResultsA BAC (B73p06) encompassing the Rhg1/Rfs2 locus was sequenced from a resistant cultivar and compared to the sequences of two susceptible cultivars from which 800 SNPs were found. Sequence alignments inferred that the resistance allele was an introgressed region of about 59 kbp at the center of which the GmRLK18-1 was the most polymorphic gene and encoded protein. Analyses were made of plants that were either heterozygous at, or transgenic (and so hemizygous at a new location) with, the resistance allele of GmRLK18-1. Those plants infested with either H. glycines or F. virguliforme showed that the allele for resistance was dominant. In the absence of Rhg4 the GmRLK18-1 was sufficient to confer nearly complete resistance to both root and leaf symptoms of SDS caused by F. virguliforme and provided partial resistance to three different populations of nematodes (mature female cysts were reduced by 30–50%). In the presence of Rhg4 the plants with the transgene were nearly classed as fully resistant to SCN (females reduced to 11% of the susceptible control) as well as SDS. A reduction in the rate of early seedling root development was also shown to be caused by the resistance allele of the GmRLK18-1. Field trials of transgenic plants showed an increase in foliar susceptibility to insect herbivory.ConclusionsThe inference that soybean has adapted part of an existing pathogen recognition and defense cascade (H.glycines; SCN and insect herbivory) to a new pathogen (F. virguliforme; SDS) has broad implications for crop improvement. Stable resistance to many pathogens might be achieved by manipulation the genes encoding a small number of pathogen recognition proteins.

Two Decades of Molecular Marker‐Assisted Breeding for Resistance to Soybean Sudden Death Syndrome

“…The RLK was shown to have an effect on reducing SCN infections with three different HgType 0s by about 30% in stable transgenics tested in three laboratories and two countries Lightfoot, 2011). Therefore, the RLK GmRLK18-1 (gene model Glyma_18_02680 at 1071 kbp on chromosome 18 of the genome sequence) was thought to be only one of several genes at the rhg1 locus active against nematodes (Cook et al, 2012;Srour et al, 2011). Therefore, the RLK GmRLK18-1 (gene model Glyma_18_02680 at 1071 kbp on chromosome 18 of the genome sequence) was thought to be only one of several genes at the rhg1 locus active against nematodes (Cook et al, 2012;Srour et al, 2011).…”

“…Three groups of scientists have independently isolated and characterized strong candidates for genes functional at the two loci (Rhg1 and Rhg4 on genetic LG-G and A2, respectively) that putatively encode resistance to SCN Cook et al, 2012;Srour et al, 2011). Three groups of scientists have independently isolated and characterized strong candidates for genes functional at the two loci (Rhg1 and Rhg4 on genetic LG-G and A2, respectively) that putatively encode resistance to SCN Cook et al, 2012;Srour et al, 2011).…”

QTLomics in Soybean: A Way Forward for Translational Genomics and Breeding

“…Ruben et al (2006) fine mapped the rhg1 locus and identified a single receptor like kinase ( RLK; leucine rich repeat transmembrane-protein kinase ) as candidate resistance gene. Srour et al (2012) characterized the GmRLK18-1 , the gene underlying Rhg1 locus, in transgenic and heterozygous plants and demonstrated that the dominant allele confers reported pleiotropic resistance to SCN and sudden death syndrome (SDS) caused by Fusarium virguliforme . In the absence of Rhg4 , the GmRLK18-1 had provided partial resistance to SCN and conferred nearly complete resistance to SDS, whereas, in the presence of Rhg4 , the plants with the GmRLK18-1 transgene were fully resistant to SCN as well as SDS (Srour et al, 2012).…”

“…Srour et al (2012) characterized the GmRLK18-1 , the gene underlying Rhg1 locus, in transgenic and heterozygous plants and demonstrated that the dominant allele confers reported pleiotropic resistance to SCN and sudden death syndrome (SDS) caused by Fusarium virguliforme . In the absence of Rhg4 , the GmRLK18-1 had provided partial resistance to SCN and conferred nearly complete resistance to SDS, whereas, in the presence of Rhg4 , the plants with the GmRLK18-1 transgene were fully resistant to SCN as well as SDS (Srour et al, 2012). In vitro , the purified LRR domain of GmRLK18-1 has been shown to bind with the CLE peptides of plant origin known to involve in tracheary element inhibition (Afzal et al, 2013).…”

“…A locus Rfs2/Rhg1 on Gm18 underlay partial resistance to the spread of root infections by F. virguliforme and SCN (Njiti et al, 1998; Triwitayakorn et al, 2005). Using NILs, Srour et al (2012) characterized Rfs2 / Rhg1 QTL on Gm18 identifying a receptor like kinase ( GmRLK18-1 ) responsible for resistance to SDS and SCN. In a GWAS study using two sets of 392 and 300 unique soybean genotypes as independent association panels, Wen et al (2014) identified a total of 20 loci underlying SDS resistance.…”