TABLE CONTENTS

Parasitism Genes of Root-Knot and Cyst Nematodes
Davis, E. (1), R. Hussey (2), M. Mitchum (3) & T. Baum (4)
(1) Department of Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA; (2) Department
of Plant Pathology, University of Georgia, Athens, GA 30602, USA; (3) Division of Plant Sciences and Bond
Life Sciences Center, University of Missouri, Columbia, MO 65211, USA; (4) Department of Plant Pathology,
Iowa State University, Ames, IA 50011, USA.
Root-knot (Meloidogyne spp.) and cyst nematodes (Heterodera and Globodera spp.) secrete
the protein products of parasitism genes (PG) expressed within their two subventral and
single dorsal esophageal gland cells from their stylet into plant tissues during host infection.
Over fifty candidate PG have been identified from both root-knot and cyst nematodes that are
differentially regulated in expression during host root penetration and subsequent
transformation of plant root cells into elaborate multinucleate feeding sites. The majority of
PG encode proteins novel to either cyst or root-knot nematodes, consistent with the
differential ontogeny of feeding cell formation between the two nematode groups. A battery
of PG that encode cell wall-modifying proteins expressed during migratory parasitic stages is
common among root-knot and cyst nematodes, including evidence that the origins of these
genes represent ancient horizontal gene transfer. The model plant species, Arabidopsis
thaliana, has been useful for functional analyses of root-knot and cyst nematode PG,
including confirmation that a Heterodera glycines PG product can mimic the function of the
endogenous plant signaling peptide CLAVATA3 that is involved in plant cell differentiation.
Both overexpression of PG in Arabidopsis and plant host-derived RNA interference (RNAi)
targeted to nematode PG are providing an assessment of the biological significance of PG
products in nematode parasitism of plants. For example, the root-knot nematode 16D10 PG
encodes a novel 13-amino acid peptide that induces accelerated root growth when
overexpressed in Arabidopsis and interacts with a specific domain of SCARECROW-like
plant transcription factors. Plant host-derived RNAi targeted to the 16D10 PG resulted in
dramatic reduction in number of females of the four major species of root-knot that
developed on plant roots, suggesting an essential role of this nematode PG product in the
parasitic interaction and a potential means of developing broad-spectrum resistance to rootknot
nematodes in multiple crop species.
5 th International Congress of Nematology, 2008 111