title: Codon usage bias and tRNA over-expression in Buchnera aphidicola after aromatic amino acid nutritional stress on its host Acyrthosiphon pisum.
abstract: Codon usage bias and relative abundances of tRNA isoacceptors were analysed in the obligate intracellular symbiotic bacterium, Buchnera aphidicola from the aphid Acyrthosiphon pisum, using a dedicated 35mer oligonucleotide microarray. Buchnera is archetypal of organisms living with minimal metabolic requirements and presents a reduced genome with high-evolutionary rate. Codonusage in Buchnera has been overcome by the high mutational bias towards AT bases. However, several lines of evidence for codon usage selection are given here. A significant correlation was found between tRNA relative abundances and codon composition of Buchnera genes. A significant codon usage bias was found for the choice of rare codons in Buchnera: C-ending codons are preferred in highly expressed genes, whereas G-ending codons are avoided. This bias is not explained by GC skew in the bacteria and might correspond to a selection for perfect matching between codon-anticodon pairs for some essential amino acids in Buchnera proteins. Nutritional stress applied to the aphid host induced a significant overexpression of most of the tRNA isoacceptors in bacteria. Although, molecular regulation of the tRNA operons in Buchnera was not investigated, a correlation between relative expression levels and organization in transcription unit was found in the genome of Buchnera.
authors.affiliation: Laboratoire de Biologie Fonctionnelle Insectes et Interactions, UMR INRA/INSA de Lyon, 203 Bâtiment Louis Pasteur, 69621 Villeurbanne Cedex, France. hubert.charles@insa-lyon.fr
authors.forename: Hubert
authors.initials: H
authors.lastname: Charles
authors.forename: Federica
authors.initials: F
authors.lastname: Calevro
authors.forename: José
authors.initials: J
authors.lastname: Vinuelas
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Fayard
authors.forename: Yvan
authors.initials: Y
authors.lastname: Rahbe
mesh_terms: D000818:Animals; D000926:Anticodon; D001042:Aphids / Q000382:microbiology*; D020635:Buchnera / Q000235:genetics* / Q000378:metabolism; D003062:Codon; D003596:Cytosine / Q000032:analysis; D004032:Diet; D015964:Gene Expression Regulation, Bacterial; D006147:Guanine / Q000032:analysis; D020411:Oligonucleotide Array Sequence Analysis; D010649:Phenylalanine / Q000378:metabolism; D012343:RNA, Transfer / Q000235:genetics* / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000926:Anticodon; D003062:Codon; D014443:Tyrosine; D010649:Phenylalanine; D006147:Guanine; D003596:Cytosine; D012343:RNA, Transfer