W596 Bioactive Plant Peptide Hormone Mimics Encoded Within Parasitic Nematode Genomes

Date: Tuesday, January 17, 2012
Time: 10:40 AM
Room: Pacific Salon 3
David McK Bird , NC State University, Raleigh, NC
Peter M DiGennaro , NC State University, Raleigh, NC
Elizabeth H Scholl , NC State University, Raleigh, NC
Nijat Imin , The Australian National University, Canberra, ACT, Australia
Michael A. Djordjevic , The Australian National University, Canberra, Australia
Michael B. Goshe , NC State University, Raleigh, NC
Valerie Williamson , University of California, Davis, Davis, CA
Charles H. Opperman , NC State University, Raleigh, NC
Meloidogyne hapla, a diploid root-knot nematode (RKN) with a compact (54 Mbp) sequenced genome (www.hapla.org), has been established as a tractable model to study the genetic and biochemical basis for plant parasitism. The current annotation freeze (HapPep4) predicts 14,207 proteins, many of which have been confirmed by LC-MSE. Comparative genomics, particularly with the sympatric RKN species M. chitwoodi and the migratory species Pratylenchus coffeae, is proving to be a powerful approach to deduce the evolution and mechanisms of parasitic ability. A current target of our functional analyses are genes encoding small proteins that exhibit sequence similarity to members of two classes of plant peptide hormones, viz., RAR (Root Architecture Regulator) and CLE (Clavata-like Elements). In M. hapla, RAR mimics are encoded by a 12-member gene family, and 8 genes encode CLE peptide mimics. Ectopic exposure of roots to RAR peptides is sufficient to elicit galling even in the absence of rhizobacteria or RKN. Further genome analysis of these loci in M. hapla supports the model that these genes were acquired from an ancestral dicot via horizontal gene transfer. We have developed bioassays to study the biology of these and other ligands involved in parasitism, and have established methods for efficient isotopic labeling of nematode proteins to empower an MS-based approach to map plant and nematode proteins.