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Title: The Tryptophan Biosynthetic Pathway of Aphid Endosymbionts (Buchnera): Genetics and Evolution of Plasmid-associated TrpEG within the Aphididae
Authors: Rouhbakhsh, D.;C.Y. Lai;M.A. Clark;L. Baumann;P. Baumann;N.A. Moran;D.J. Voegtlin
Contributors: 生物系
Keywords: Aphid�;Buchnera aphidicola;�Cospeciation�;Endosymbiosis�;�Mutualism;Tryptophan biosynthesis�;trpEG;trpB;�Gene amplification;�Plasmid evolution
Date: 1996-04
Issue Date: 2011-05-16T07:39:20Z
Publisher: Springer Verlag
Abstract: The bacterial endosymbionts (Buchnera) from the aphidsRhopalosiphum padi, R. maidis, Schizaphis graminum, andAcyrthosiphon pisum contain the genes for anthranilate synthase (trpEG) on plasmids made up of one or more 3.6-kb units. Anthranilate synthase is the first as well as the rate-limiting enzyme in the tryptophan biosynthetic pathway. The amplification oftrpEG on plasmids may result in an increase of enzyme protein and overproduction of this essential amino acid, which is required by the aphid host. The nucleotide sequence oftrpEG from endosymbionts of different species of aphids is highly conserved, as is an approximately 500-bp upstream DNA segment which has the characteristics of an origin of replication. Phylogenetic analyses were performed usingtrpE andtrpG from the endosymbionts of these four aphids as well as from the endosymbiont ofSchlechtendalia chinensis, in whichtrpEG occurs on the chromosome. The resulting phylogeny was congruent with trees derived from sequences of two chromosome-located bacterial genes (part oftrpB and 16S ribosomal DNA). In turn, trees obtained from plasmid-borne and bacterial chromosome-borne sequences were congruent with the tree resulting from phylogenetic analysis of three aphid mitochondrial regions (portions of the small and large ribosomal DNA subunits, as well as cytochrome oxidase II). Congruence of trees based on genes from host mitochondria and from bacteria adds to previous support for exclusively vertical transmission of the endosymbionts within aphid lineages. Congruence with trees based on plasmid-borne genes supports the origin of the plasmid-bornetrpEG from the chromosomal genes of the same lineage and the absence of subsequent plasmid exchange among endosymbionts of different species of aphids.
Relation: Journal of Molecular Evolution, 42(4):414-421
Appears in Collections:[生物技術研究所] 期刊論文

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