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Abstract

Pristionchus pacificus represents a nematode that shares with Caenorhabditis elegans many technical features and has been developed as a model system in evolutionary developmental biology. Many important differences on the genetic and molecular level of development, in particular vulva development, have been identified (for review see Hong & Sommer, BioEssays, 2006). Intriguingly, Pristionchus also occupies a distinct ecological niche. Pristionchus nematodes are associated with scarab beetles and have a necromenic life style: that is, worms invade the beetle as dauer larvae and wait for the insect's death to feed on the developing microbes on the carcass. It has been suggested that a close association with other organisms as seen in necromenic nematodes represent a pre-adaptation towards true parasitsm. The P. pacificus California strain was selected as reference strain for high-coverage sequencing and the Washington strain was selected for low-coverage sequencing because it interbreeds with the California strain. The assembly of the P. pacificus California genome attains 9-10 fold coverage and is divided into 2,894 supercontigs. It contains 145 Mb of unique sequence and calculates a total genome size of around 169 Mb. The Washington polymorphic strain differs from the reference strain on average in 4.3% of all un-gapped positions in a whole genome alignment. With 169-Mb and 29,000 predicted protein-coding genes the P. pacificus genome is substantially larger than the genomes of Caenorhabditis elegans and the human parasite Brugia malayi. Comparative analysis with C. elegans revealed an elevated number of genes encoding cytochrome P450 enzymes, glucosyl-transferases and ABC transporters that were experimentally validated and confirmed. P. pacificus contains cellulase and diapausin genes and cellulase activity is found in P. pacificus secretions, the first time cellulases have been identified in nematodes beyond plant parasites. The increase in detoxification and degradation enzymes is consistent with the Pristionchus life-style and is a pre-requisite for parasitism. Thus, comparative genomics of three ecologically distinct nematodes offers a unique opportunity to investigate the correlation between genome structure and life-style. Current studies involve developmental and genetic analysis of various traits associated with the specific ecological setting of P. pacificus, such as dauer formation, insect recognition by olfaction, mouth form dimorphism and bacterial association. The talk will provide an overview on recent studies in P. pacificus genomics, proteomics and ecology.