Abstract
The proteobacterium Buchnera aphidicola and its aphid hosts have a symbiotic relationship, in which B. aphidicola provides its hosts with essential amino acids. In the case of tryptophan, Buchnera carries genes for the biosynthesis of tryptophan on both its chromosomes (trpB and dnaN) and on plasmids (trpEG). To explore the evolution of B. aphidocola in Myzus persicae (Sulzer), we determined the partial sequences of trpB, dnaN and trpEG from B. aphidicola of four Chinese populations of M. persicae. These genes were found to have characteristics of the corresponding genes in B. aphidicola strains in other aphids. The trpB gene sequence in M. persicae was more closely related to that in Diuraphis noxia, and dnaN and trpEG genes were in the same clade as D. noxia. The phylogenies inferred from trpB, dnaN and trpEG were largely concordant, reflecting the systematics of the host aphids.
