What does a worm want with 20,000 genes? The evolution of plant-parasitism, and the essential-gene conundrum.

D. McK. Bird¹, E. S. Scholl².

(1) Center for the Biology of Nematode Parasitism, (2) Bioinformatics Research Center, North Carolina State University, Raleigh NC 27695.

The fully-sequenced genome of bacterivorous nematode C. elegans encodes 20,000 protein and RNA genes. The largest gene family (approximately 1,000 members) encodes G-protein-coupled receptors, many of which are olfactory receptor, indicative of the sophistication with which nematodes interact with the environment. Unlike lab-reared C. elegans for which many of the genes are dispensable, behavioral and other aspects of their lifestyle render many of these non-essential genes as being essential in parasites. EST-sequencing projects have revealed many orthologs of C. elegans genes in plant-parasites, including some apparently nematode-specific sequences. Some genes expressed by plant parasites are absent from C. elegans, including a cadre of genes apparently acquired from microbes. We are endeavoring to experimentally- validate our computational predictions of horizontal gene-transfer, and speculate that such events played crucial roles in speciation of plant-parasitic nematodes.

 

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