The hepta--glucoside elicitor, (HG), consisting of 16, 13-- linkages is derived from glucans found in the cell wall of the pathogen, Phytophthora sojae. The HG is capable of eliciting defense responses in legumes leading to phytoalexin production. High affinity -glucan-binding sites (GBPs) for the HG elicitor found in soybean have been shown to be plasma-membrane protein complexes. The soybean GBP also has glucanohydrolic properties toward -1,3 glucans found in pathogen cell walls. This project had two principal goals. First, to clone full-length cDNA sequences corresponding to three EST contig sequences (MtKV0, MtKV2, and MtKV3) from Medicago truncatula that are highly similar to the soybean GBP and to study the expression patterns of these genes in M. truncatula tissues. The full-length cDNA sequence for MtKV3 was determined. Gene expression studies in eight wild type tissues demonstrated that MtKV0, MtKV2, and MtKV3 are most highly expressed in roots. The second goal was to identify and characterize single nucleotide polymorphisms (SNPs) leading to amino acids changes in MtKV3 that might alter the glucanohydrolytic properties of this protein. The wild type and mutant genes were expressed in Nicotiana benthamiana. One mutant protein lost glucan hydrolytic activity suggesting amino acid variations in one of the putative conserved glucanase domains could be responsible for the loss of activity.
