Shared Metabolic Pathways in a Coevolved Insect-Bacterial Symbiosis

摘要: The symbiotic bacterium Buchnera aphidicola lacks key genes in the biosynthesis of five essential amino acids (EAAs), and yet its animal hosts (aphids) depend on symbiosis for synthesis these EAAs (isoleucine, leucine, methionine, phenylalanine, valine). We tested hypothesis, derived from genome annotation, that missing reactions are mediated by host enzymes, with exchange metabolic intermediates between partners. specialized cells bearing were separated into a fraction Buchnera-free cell (HF). Addition HF to isolated preparations significantly increased production leucine recombinant enzymes mediating final branched-chain acid phenylalanine rescued without HF. likely precursors proximal isoleucine methionine identified, they differed predictions based annotations: 2-oxobutanoate, aphid-derived precursor synthesis, was stimulated homoserine not threonine via dehydratase, homocysteine driven cystathionine, cysteine, reversal transsulfuration pathway. evolution shared pathways this can be attributed compensation genomic deterioration symbiont, involving changes gene expression networks recruit specific cell.