With regard to the nematode, we have been focusing on the identification and functional analysis of nematode genes encoding esophageal gland secretions (i.e. nematode parasitism genes) as part of a Molecular Nematology collaboration with the labs of Dr. Eric Davis (NCSU), Dr. Dick Hussey (UGA), Dr. Thomas Baum (ISU), and Dr. Xiaohong Wang (Cornell). Our group is interested in elucidating the underlying mechanisms of cyst nematode parasitism, in particular how cyst nematodes utilize esophageal gland secretions to modify plant cells during the formation of a complex feeding site (syncytium) within the host root, which is required for their growth and development.
It is unclear how feeding sites are induced by the nematode and the nature and origin of the stimulus required to elicit the formation of feeding sites has not been identified. However, evidence suggests that nematode esophageal gland secretions are key molecules involved in initiating the interaction and modifying plant cells for parasitism. Notable progress has been made to determine the identity and nature of the molecules involved in establishing the parasitic interaction. Previously, nematode esophageal gland cell-specific cDNA libraries were constructed from microaspirated gland cell mRNA using PCR-based approaches and subjected to extensive EST sequence analysis. My laboratory is using molecular genetic approaches to conduct functional analyses of some of these parasitism gene products to determine their role in plant parasitism. Approaches include RNA interference, ectopic expression in plants, and protein-protein interaction studies. Of particular interest is a class of Heterodera genes encoding secreted CLAVATA3/ESR-like (CLE) peptides and we are currently conducting detailed functional studies to assess the role of ligand mimicry in plant parasitism. We have also identified differences in the molecular structure of parasitism gene products among H. glycines genotypes that correlate with virulence on resistant soybean and are examining a potential role for these proteins in eliciting, suppressing or evading host plant resistance mechanisms.