TABLE CONTENTS

Genes Expressed during the Early Stages of Infection by the
Entomopathogenic Nematodes Heterorhabditis bacterioprhora and
Steinernema carpocapsae
Burnell, A.M. (1), Z. Mulroy Hehir (1), K.M. Dolan (1,2) & J.T. Jones (3)
(1) Biology Department, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland; (2) Applied
Biosystems, Lingley House, 120 Birchwood Boulevard, Warrington, Cheshire, WA3 7QH, UK; (3) Plant-
Pathogen Interactions Programme, Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, UK.
The dauer juvenile stage (DJ) stages of the entomopathogenic nematodes (EPN)
Heterorhabditis and Steinernema are adapted for dispersal, host finding and infection. Once
inside the infected insect the DJs release cells of a bacterial symbiont which they carry in
their intestines. The genome of Photorhabdus luminescens, the symbiont bacterium of
Heterorhabditis bacteriophora has been sequenced (Duchaud et al., 2003). Analysis of this
genome indicates the importance of this symbiont’s role in insect killing and bioconversion
of the insect cadaver into a suitable food medium, as it encodes a large number and variety of
toxins and lytic enzymes. The genome of H. bacteriophora is currently being sequenced
(http://genome.wustl.edu/genome.cgi/). H bacteriophora needs its symbiont (Photorhabdus
luminescens) to kill its insect host, but axenised Steinernema carpocapsae are able to infect
and kill insects unaided. Thus it seems that S. carpocapsae produces the necessary
insecticidal toxins independently of its bacterial symbiont. The genome of Xenorhabdus
nematophila the bacterial symbiont of S. carpocapsae is currently being sequenced
(http://xenorhabdus.danforthcenter.org/), but no Steinernema genome sequencing project has
been initiated to date. We tested the ability of S. carpocapsae strains from around the world,
when cultured axenically, to kill insect larvae. The most virulent was found to be the Breton
(France) isolate. We constructed a cDNA library from S. carpocapsae DJs 4 hours post
infection. We sequenced 4608 ESTs from this library. Abundant and novel nematode
sequences also some proteases and elastase that have predicted signal peptides were selected
from this dataset for further investigation. The entire library of 15,360 clones was spotted
onto high density filters. These have been probed with radiolabelled cDNA from Breton
strain 4 hours after recovery and also with cDNAs from non-recovered Breton DJs and from
an avirulent strain of S. carpocapsae. In our presentation we will provide a summary of these
analyses.
5 th International Congress of Nematology, 2008 110