A Soybean Cyst Nematode Resistance Gene Points to a New Mechanism of Plant Resistance to Pathogens

Soybean cyst nematode is a devastating pest of soybean that causes more than one billion dollars in annual yield losses in the US alone. We report the map-based cloning of a gene at the Rhg4 (for resistance to Heterodera glycines4) locus, a major quantitative trait locus contributing to resistance to this pathogen. Mutation analysis, gene knock-down studies, and transgenic complementation confirmed that the gene confers resistance. The gene encodes a serine hydroxy-methyltransferase, an enzyme ubiquitous in nature, structurally conserved across kingdoms, which is responsible for interconversion of serine and glycine and thus essential for cellular one-carbon metabolism. This discovery has unveiled an unprecedented plant resistance mechanism against a pathogen. Alleles of Rhg4 conferring resistance or susceptibility differ by two genetic polymorphisms predicted to compromise folate binding affinity of the resistant allele. The mechanistic knowledge of the resistance gene can now be readily exploited to improve nematode resistance of soybean, an increasingly important global crop.