Present address: US Agency for International Development, Bureau of Economic Growth, Agriculture, and Trade, Office of Environment and Science Policy, Washington DC 20523, USA. This whole Genome Shotgun project has been deposited at DDBJ/EMBL/GenBank under the accession ACYF00000000. The version described in this paper is the first version, ACYF01000000.
Dynamics of genome evolution in facultative symbionts of aphids
Article first published online: 16 OCT 2009
© 2009 Society for Applied Microbiology and Blackwell Publishing Ltd
Special Issue: Symbiosis. Editors: Professors Paola Bonfante, Karen Visick, and Moriya Ohkuma
Volume 12, Issue 8, pages 2060–2069, August 2010
How to Cite
Degnan, P. H., Leonardo, T. E., Cass, B. N., Hurwitz, B., Stern, D., Gibbs, R. A., Richards, S. and Moran, N. A. (2010), Dynamics of genome evolution in facultative symbionts of aphids. Environmental Microbiology, 12: 2060–2069. doi: 10.1111/j.1462-2920.2009.02085.x
Re-use of this article is permitted in accordance with the Terms and Conditions set out at http://www3.interscience.wiley.com/authorresources/onlineopen.html
- Issue published online: 4 AUG 2010
- Article first published online: 16 OCT 2009
- Received 9 June, 2009; accepted 2 September, 2009.
Aphids are sap-feeding insects that host a range of bacterial endosymbionts including the obligate, nutritional mutualist Buchnera plus several bacteria that are not required for host survival. Among the latter, ‘Candidatus Regiella insecticola’ and ‘Candidatus Hamiltonella defensa’ are found in pea aphids and other hosts and have been shown to protect aphids from natural enemies. We have sequenced almost the entire genome of R. insecticola (2.07 Mbp) and compared it with the recently published genome of H. defensa (2.11 Mbp). Despite being sister species the two genomes are highly rearranged and the genomes only have ∼55% of genes in common. The functions encoded by the shared genes imply that the bacteria have similar metabolic capabilities, including only two essential amino acid biosynthetic pathways and active uptake mechanisms for the remaining eight, and similar capacities for host cell toxicity and invasion (type 3 secretion systems and RTX toxins). These observations, combined with high sequence divergence of orthologues, strongly suggest an ancient divergence after establishment of a symbiotic lifestyle. The divergence in gene sets and in genome architecture implies a history of rampant recombination and gene inactivation and the ongoing integration of mobile DNA (insertion sequence elements, prophage and plasmids).