TABLE CONTENTS

Comparative Genomics of Meloidogyne: Genome Reorganization on the
Road to Plant Parasitism
Bird, D.McK., C.H. Opperman & the M. hapla Genome Annotation Team
Center for the Biology of Nematode Parasitism, North Carolina State University, Raleigh, NC 27695, USA
Meloidogyne spp. are the most damaging and economically significant plant-parasitic
nematodes worldwide. We selected M. hapla for sequencing based on its small genome (54
Mbp) and established genetic system (sexually reproducing diploid) and have obtained a
whole genome assembly that spans >97% of the M. hapla genome. Extensive automatic and
manual annotation has revealed that M. hapla encodes ~14,500 genes. In addition to gene
discovery, a major motivation for sequencing plant-parasitic nematode genomes is to
understand the processes that have lead to adaptation to the parasitic life style. Comparison of
the genome sequence of M. hapla with those of other nematodes, including the non-parasitic
species C. elegans, has revealed a pattern of gene loss and gene gain reflecting selective
pressures both on individual genes and also on more substantial chromosomal reorganization;
the role of these processes in the evolution of the genus will be discussed. The completion of
the M. incognita genome by Abad et. al., coupled with partial genomes from cyst nematodes
and those of other animal-parasitic and free-living nematodes, provides a unique platform for
comparative genomics among the plant-parasitic Nematoda.
Worm and Fly: What Whole Genome Comparisons Can Tell Us about
Taste and Smell
Trowell, S.
CSIRO Food Futures Flagship & CSIRO Entomology, Canberra, ACT 2601, Australia
Caenorhabditis elegans has 32 chemosensory neurons and possibly as few as eight
interneurons dedicated to processing chemosensory information 1 . In contrast, Drosophila
melanogaster, which has the simplest olfactory system of any insect studied in depth, has
more than 2,500 chemosensory neurons 2 and at least twice that number of interneurons 3
dedicated to processing chemosensory information. Neural networks that match the scale of
the Drosophila mushroom bodies are capable of robust classification of many tens or even
hundreds of input classes 4 but it is not conceivable that the nervous system of C. elegans has
this level of integrative power. Despite theory suggesting that the lack of neural processing
power will impose severe restrictions on the nematode’s ability to identify and discriminate
amongst chemosensory cues, the nematode displays a range of sophisticated chemosensory
behaviours, raising the question of how this is achieved. Approximately 1,500
chemoreceptor genes have been identified in the genome sequence of C. elegans, a seemingly
extravagant number compared with the 62 olfactory receptor genes and 60 gustatory receptor
genes known from D. melanogaster. It may be that the nematode’s larger repertoire of
chemoreceptor genes reflects a radically different chemosensory architecture from insects and
more complex animals. If so, it would lead to some precise predictions regarding the
molecular pharmacology of nematode ORs. Furthermore, the real-time performance of even
such a modest nervous system as that of D. melanogaster cannot yet be replicated in silico
cost effectively. Therefore chemosensing strategies adopted by the nematode may provide
some useful learnings for human engineers.
1
P. Sengupta, Pflugers Arch 454 (5), 721 (2007).
2
3
4
M. de Bruyne and C. G. Warr, BioEssays 28 (1), 23 (2006).
R. L. Davis, Neuron 11 (1), 1 (1993).
T. Nowotny, R. Huerta, H. D. Abarbanel et al., Biol Cybern 93 (6), 436 (2005).
5 th International Congress of Nematology, 2008 88