Submitted to: Veterinary Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/10/2008
Publication Date: 2/23/2009
Citation: Zarlenga, D.S., Rosenthal, B.M., Hoberg, E.P., Mitreva, M. 2009. Integrating genomics and phylogenetics in understanding the history of trichinella species. Veterinary Parasitology. 159(3-4):210-3. Interpretive Summary: The adenophorean nematodes are the most evolutionarily distant group from the other classically studied species in the phylum Nematoda such as Caenorhabditis elegans. The genus Trichinella represents a basal or outgroup adenophorean for genome sequencing and for gaining deeper insight into the evolution of nematodes. Nematode characteristics that are universally conserved across the phylum could have a great value for control strategies with broad application. Herein we evaluate preliminary genome sequence data on Trichinella spiralis the most widespread within this genus. This data was used to investigate specific questions related to the biology of T. spiralis and more generally to parasitic nematodes. This information, and that yet to come in conjunction with the relatively recent diversification of contemporary species provides expectations that this genome sequence will advance research related to parasitic nematodes across the phylum, and will assist in developing conserved control strategies currently unattainable due to the dearth of genetic information relating these organisms.
Technical Abstract: In 2004, funding was received by Washington University’s Genome Sequencing Center through NHGRI, to completely sequence several nematode genomes as part of a holistic effort to advance our understanding of the human genome and evolution within the Metazoa. Trichinella spiralis was among this group of worms because of its strategic location at the base of the phylum Nematoda, and the belief that extant species represented an ancient divergent event that occurred as early as the Paleozoic. At the same time, a concerted effort was put forth to solidify the phylogeny of extant species of Trichinella based upon molecular analyses of a multi-gene system to understand the history of the genus and thereby enhance utilization of the forthcoming sequence data. Since the inception of this research, several findings have emerged; 1) the size of T. spiralis genome estimated by flow cytometry (71.3 Mb) is substantially smaller than originally predicted (270 Mb); 2) to date, a subset of the total of 3,534,683 sequences have been assembled into a 59.3 Mb unique sequence; 3) 19% of the assembled sequence is comprised of repetitive elements, and; 4) sequence data is predicated upon extant Trichinella spiralis which probably diverged as little as 20 million years ago. Thus, the utility of the T. spiralis genome as representative of an archaic species must be tempered with the knowledge that encapsulated and non-encapsulated clades probably separated during the mid-Miocene as temperate ecosystems changed.