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Dynamics of genome evolution in facultative symbionts of aphids
Author(s) -
Degnan Patrick H.,
Leonardo Teresa E.,
Cass Bodil N.,
Hurwitz Bonnie,
Stern David,
Gibbs Richard A.,
Richards Stephen,
Moran Nancy A.
Publication year - 2010
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2009.02085.x
Subject(s) - buchnera , biology , genome , prophage , gene , genetics , candidatus , obligate , bacterial genome size , host (biology) , genome evolution , evolutionary biology , bacteriophage , ecology , escherichia coli
Summary 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).