MOLECULAR CHARACTERIZATION AND PHYLOGENETIC EVALUATION OF THE HSP90 GENE FROM SELECTED NEMATODES

Authors: Skantar, Andrea; Carta, Lynn

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2004
Publication Date: 12/1/2004
Citation: Skantar, A.M., Carta, L.K. 2004. Molecular characterization and phylogenetic evaluation of the hsp90 gene from selected nematodes. Journal of Nematology 36: 466-480.

Interpretive Summary: Crop-feeding nematodes are microscopic worms that cause an estimated ten billion dollar annual loss to U.S. agriculture. Regulatory agencies that monitor the safety of imported and exported crops must rely on swift and accurate identification of plant-parasitic nematodes from quarantine samples. A problem with nematode identification is that there are few anatomical features useful for distinguishing one species from another. Therefore, we are developing molecular methods for diagnosing nematode species. In this paper, the molecular tool examined as a diagnostic molecule is a gene called hsp90 that codes for a heat shock protein involved in nematode response to environmental extremes. We discovered that regions not coding for protein had species-specific gene arrangements and genus-specific sizes. Major protein-coding sequence differences occurred between species and minor differences within. These studies are significant because they demonstrate that hsp90 is a useful new character for diagnosis of plant-parasitic nematodes and for establishing the evolutionary relationships between nematodes, and the relationship of nematodes to other organisms. The results will be used by scientists in developing rapid and reliable methods of identifying nematodes.

Technical Abstract: Novel molecular traits are needed for the phylogenetic comparison of plant-parasitic nematodes and for diagnostic purposes, particularly in circumstances where source specimens are limited, or when currently used molecules such as rDNA genes do not exhibit the level of molecular discrimination required to distinguish genera, species, or isolates. Therefore, we set out to develop the hsp90 gene as a novel diagnostic molecule for selected nematodes. Degenerate primer PCR was used to amplify hsp90 gene sequences from representatives of several plant-parasitic nematode genera, including Heterodera, Meloidogyne, Pratylenchus, and Bursaphelenchus. Alignment of partial hsp90 genomic DNA sequences revealed that hsp90 introns had species-specific arrangements and genus-specific sizes. Analysis of protein-coding sequences showed that major protein-coding sequence differences occurred between species with minor sequence differences occurring within species. Comparison of nematode HSP90 protein sequences with those from other organisms revealed several nematode-specific amino acid residues. These studies demonstrate that hsp90 is a useful new character for diagnosis of plant-parasitic nematodes and for establishing the evolutionary relationship between nematodes and other organisms.