A correlation between host-mediated expression of parasite genes as tandem inverted repeats and abrogation of development of female Heterodera glycines cyst formation during infection of Glycine max.

Host-mediated (hm) expression of parasite genes as tandem inverted repeats was investigated as a means to abrogate the formation of mature Heterodera glycines (soybean cyst nematode) female cysts during its infection of Glycine max (soybean). A Gateway-compatible hm plant transformation system was developed specifically for these experiments in G. max. Three steps then were taken to identify H. glycines candidate genes. First, a pool of 150 highly conserved H. glycines homologs of genes having lethal mutant phenotypes or phenocopies from the free living nematode Caenorhabditis elegans were identified. Second, annotation of those 150 genes on the Affymetrix soybean GeneChip allowed for the identification of a subset of 131 genes whose expression could be monitored during the parasitic phase of the H. glycines life cycle. Third, a microarray analyses identified a core set of 32 genes with induced expression (>2.0-fold, log base 2) during the parasitic stages of infection. H. glycines homologs of small ribosomal protein 3a and 4 (Hg-rps-3a [accession number CB379877] and Hg-rps-4 [accession number CB278739]), synaptobrevin (Hg-snb-1 [accession number BF014436]) and a spliceosomal SR protein (Hg-spk-1 [accession number BI451523.1]) were tested for functionality in hm expression studies. Effects on H. glycines development were observed 8 days after infection. Experiments demonstrated that 81-93% fewer females developed on transgenic roots containing the genes engineered as tandem inverted repeats. The effect resembles RNA interference. The methodology has been used here as an alternative approach to engineer resistance to H. glycines.