Submitted to: Comparative Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2004
Publication Date: 5/1/2005
Citation: Kovaleva, E.S., Subbotin, S.A., Masler, E.P., Chitwood, D.J. 2005. Molecular characterization of the actin gene from cyst nematodes in comparison with those from other nematodes. Comparative Parasitology. 72(1): 39-49. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack all crops of agricultural importance, causing over $10 billion in losses annually to U.S. farmers. One problem facing growers is that environmental concerns will eliminate in a few years the most extensively used chemical used to kill nematodes in the United States. This makes the discovery of environmentally and economically sound replacements critical. One approach is to identify natural targets in nematodes that can be used to develop novel control approaches. In this paper we report the discovery of an important gene called the actin gene in the soybean cyst nematode, the most serious pest of soybeans in the United States. Actin is a protein essential for nematode development, survival, feeding and reproduction. This discovery is significant because it is the first report of this gene in any plant-parasitic nematode, and the importance of the gene makes it a prime natural target at which to focus development of a variety of natural control strategies. This information will be used by researchers who are developing safe, selective and cutting-edge methods for nematode control.
Technical Abstract: Actin is an abundant, highly expressed and very conserved protein from the actin/heat shock protein70/sugar kinase superfamily. The full-length mRNA encoding actin was cloned and characterized from the plant-parasitic cyst nematodes Heterodera glycines and Globodera rostochiensis, and from the free-living nematode Panagrellus redivivus. The predicted amino acid sequences of the plant nematode actins showed highest amino acid sequence identity to filarial nematode homologues, whereas their nucleotide sequence identity was much lower than that to many actins from very distant organisms, such as vertebrates, plants or fungi. Analysis of base composition revealed a striking difference between the H. glycines actin gene and those of filarial nematodes in (G+C) content and usage of particular codons. Analysis of genomic DNA disclosed the presence of seven introns in the H. glycines actin gene, the first of which was atypically long and started with a GC dinucleotide. Two other introns occupy the novel sites in the catalogue of positions known thus far for actin genes. Phylogenetic comparisons of actins known from animal-parasitic, plant-parasitic and free-living nematodes were generated with three independent parameters (amino acid sequences, base composition and gene structure) and are discussed.