(A) Construction of plasmid pCMPG10652. Constitutive promoter P A , gene hpaA , and 4-Hydroxyphenylacetic acid (4-HPA) responsive promoter P BC were copied from plasmid pRA 2 (Prieto and García, 1997 ) and placed in plasmid pFPV25 (Valdivia and Falkow, 1996 ), upstream of gene gfp . This yields GFP production controlled by 4-HPA and 2-Phenylacetic Acid (PAA) concentrations, detected by HpaA. (B) Fluorescence measurements of GFP production of strain pCMPG10652/ E. coli TOP10 in response to a range of 4-HPA concentrations. (C) Fluorescence measurements of GFP production of strain pCMPG10652/ E. coli TOP10 in response to a range of PAA concentrations. Auxin concentrations used in fluorescence measurements: 3 mM, 2 mM, 1.5 mM, 1 mM, 500 μM, 250 μM, 125 μM, 62 μM, 31.25 μM, 15.625 μM, and 0M. n = 8 per measured concentration.