Genome Sequence of the Pea Aphid Acyrthosiphon pisum
The schematic shows hypothetical relations based on the annotation of amino acid biosynthesis genes in the two organisms. Buchnera cells are located in the cytoplasm of specialized aphid cells, known as bacteriocytes. Each Buchnera cell is bound by three membranes, interpreted as the inner bacterial membrane (brown), outer bacterial membrane (green), and a membrane of insect origin known as the symbiosomal membrane (purple). The predicted biosynthesis (dark arrows) of essential amino acids (purple) and nonessential amino acids (green) and transport (light arrows) of metabolites between the partners are shown. The thickness of dark arrows indicates the number of metabolic reactions represented; thin arrows represent a single reaction and thick arrows more than one reaction. *The amino acid Gly appears twice in the Buchnera cell because it is synthesized by both Buchnera and the aphid (and possibly taken up by Buchnera). Metabolite abbreviations appear as follows: 2obut, 2-oxobutanoate; 3mob, 3-methyl-2-oxobutanoate; 3mop, (S)-3-methyl-2-oxopentanoate; 4mop, 4-methyl-2-oxopentanoate; e4p, D-erythrose 4-phosphate; hcys-L, homocysteine; pep, phosphoenolpyruvate; phpyr, phenylpyruvate; prpp, phosphoribosyl pyrophosphate; pyr, pyruvate.