FIG 2.

Histidine biosynthesis in isogenic aphid lines bearing Hamiltonella (SC_583) and lacking Hamiltonella (SC_583^H-). (A) AICAR is a metabolic by-product of histidine biosynthesis in Buchnera. Reactions for de novo purine biosynthesis are absent (dashed arrows indicate genes missing from the Buchnera genome), and purines are instead synthesized from AICAR, which is a by-product of histidine biosynthesis in Buchnera. Abbreviations: PRPP, phosphoribosyl pyrophosphate; 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR); IMP, inosine monophosphate. (B) Incorporation of dietary [¹³C₆]histidine, determined as the ratio of [¹³C]histidine to [¹²C]histidine into aphid soluble pools and hydrolyzed protein pools. (C) Corrected peak area of AICAR and total soluble histidine (all measurable isotopes combined) of aphids. Statistical tests applied the critical probability of 0.025, following Bonferroni correction for two tests. s.e., standard error.