Hansen AK, Moran NA.. Altered tRNA characteristics and 3' maturation in bacterial symbionts with reduced genomes. Nucleic Acids Res 40: 7870-7884

Department of Ecology and Evolutionary Biology, West Campus, Yale University, PO Box 27388 West Haven, CT 06516-7388, USA.
Nucleic Acids Research (Impact Factor: 9.11). 06/2012; 40(16):7870-84. DOI: 10.1093/nar/gks503
Source: PubMed


Translational efficiency is controlled by tRNAs and other genome-encoded mechanisms. In organelles, translational processes
are dramatically altered because of genome shrinkage and horizontal acquisition of gene products. The influence of genome
reduction on translation in endosymbionts is largely unknown. Here, we investigate whether divergent lineages of Buchnera aphidicola, the reduced-genome bacterial endosymbiont of aphids, possess altered translational features compared with their free-living
relative, Escherichia coli. Our RNAseq data support the hypothesis that translation is less optimal in Buchnera than in E. coli. We observed a specific, convergent, pattern of tRNA loss in Buchnera and other endosymbionts that have undergone genome shrinkage. Furthermore, many modified nucleoside pathways that are important
for E. coli translation are lost in Buchnera. Additionally, Buchnera’s A + T compositional bias has resulted in reduced tRNA thermostability, and may have altered aminoacyl-tRNA synthetase recognition
sites. Buchnera tRNA genes are shorter than those of E. coli, as the majority no longer has a genome-encoded 3' CCA; however, all the expressed, shortened tRNAs undergo 3′ CCA maturation.
Moreover, expression of tRNA isoacceptors was not correlated with the usage of corresponding codons. Overall, our data suggest
that endosymbiont genome evolution alters tRNA characteristics that are known to influence translational efficiency in their
free-living relative.

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