Fig. 1. Specific amino acids (AAs) are essential for 20-hydroxyecdysone (20E)-activation of the vitellogenin (vg) gene. Fat bodies from 3- to 5-day-old mosquitoes were cultured for 3 h at 27°C in media lacking individual AAs in the presence of 20E (10^-6 mol l^-1). Total RNA was isolated from three groups of six fat bodies per treatment. cDNA was synthesized from equal amounts of DNase I-treated total RNA. Real-time PCR was used to quantify levels of vg mRNA. Data was normalized by real-time PCR analysis of actin levels in the cDNA samples. vg production in responses to 20E stimulation in the `withdrawal' medias are presented as the mean percentage (± s.e.m. of triplicate samples) relative to the response observed in the control medium containing complete AAs.