Modulations in gene expression and mapping of genes associated with cyst nematode infection of soybean

Infection of the soybean root by the soybean cyst nematode (SCN) (Heteroder a glycines Ichinohe) induces a well-documented, yet poorly understood, resp onse by the host plant. The plant response, involving the differentiation o f a feeding structure, or "syncytium," facilitates the feeding and reproduc tion of the nematode to the detriment of the host. We used a genetic system involving a single dominant soybean gene conferring susceptibility to an i nbred nematode strain, VL1, to characterize the nematode-host interaction i n susceptible line PI 89008, The restriction fragment length polymorphism m arker pB053, shown to map to a major SCN resistance locus, cosegregates wit h resistance among F-2 progeny from the PI 89008 x PI 88287 cross. Cytologi cal examination of the infection process confirmed that syncytium developme nt in this genetic system is similar to that reported by others who used no ninbred nematode lines. Our study of infected root tissue in the susceptibl e line PI 89008 revealed a number of genes enhanced in expression. Among th ese are catalase, cyclin, elongation factor 1 alpha, beta -1,3-endoglucanas e, hydroxymethylglutaryl coenzyme A reductase, heat shock protein 70, late embryonic abundant protein 14, and formylglycinamidine ribonucleotide synth ase, all of which we have genetically positioned on the public linkage map of soybean, Formylglycinamidine ribonucleotide synthase was found to be tig htly linked with a major quantitative trait locus for SCN resistance. Our o bservations are consistent with the hypothesis proposed by others that feed ing site development involves the dramatic modulation of gene expression re lative to surrounding root cells.