Discovery of Genes and Networks Regulating Soybean Cyst Nematode Resistance

Soybean cyst nematode (SCN; Heterodera glycines Ichinohe) is a microscopic roundworm that feeds on the roots of soybean and is a major constraint to soybean production. Management relies heavily on the deployment of resistant soybean cultivars. However, our current lack of understanding of the molecular basis of soybean resistance to this nematode continues to hinder progress to enhance the effectiveness and durability of natural plant resistance and enable the design of novel resistance strategies. We are interested in the network of molecular events that underlie incompatible SCN-soybean interactions. A map-based cloning approach, coupled with newly developed functional genomic tools in soybean, led to the identification of a serine hydroxymethyltransferase gene at the Rhg4 (for resistance to Heterodera glycines 4) locus in resistance to this pathogen. Plants carrying Rhg genes display an incompatible interaction between host and parasite. The plant’s roots are penetrated by infective juveniles, but feeding cells induced by the nematodes to serve as their sole nutritive source, degenerate prematurely. Laser capture microdissection coupled with transcript profiling has enabled the identification of soybean genes whose expression coincides with feeding cell degeneration in resistant cultivars. A multi-pronged approach targeted at both the host and pathogen and using a combination of mutants, RNAi, VIGS, overexpression, next generation sequencing, and metabolome analysis are underway to discover additional genes and networks regulating SCN resistance. These findings will help to develop a mechanistic understanding of the plant’s resistance against this important parasite of soybean.