Vertical transmission of biosynthetic plasmids in aphid endosymbionts (Buchnera)

This study tested for horizontal transfer of plasmids among Buchnera aphidi cola strains associated with ecologically and phylogenetically related aphi d hosts (Uroleucon species). Phylogenetic congruence of Buchnera plasmid (t rpEG and leuABC) and chromosomal (dnaN and trpB) genes supports strictly ve rtical long-term transmission of plasmids, which persist due to their contr ibutions to host nutrition rather than capacity for infectious transfer. Sy nonymous divergences indicate elevated mutation on plasmids relative to chr omosomal genes.