Prenyltransferases play a key role in isoprenoid biosynthesis. Here, a cDNA encoding a prenyltransferase was isolated from the cotton aphid, Aphis gossypii, which consists of 1354 nucleotides and encodes a protein of 394 amino acids (AgIPPS). Subsequent sequencing of AgIPPS genomic DNA resulted in one 3138-bp sequence. Southern blotting analysis indicated that only a single IPPS gene exists in the cotton aphid. Real-time quantitative PCR showed that AgIPPS transcripts were mainly present at the corpora allatum, but small quantity could be detected in tissues other than the corpora allatum. Transcript abundance changed in an alternative manner at different life stages. High expression was observed in embryos, second and forth instar nymphs and adults, but only low level was detected in the first and third instars. Functional expression, activity assay and product analysis revealed that the mature form of AgIPPS (AgIPPS-S) could efficiently convert labeled isopentenyl diphosphate in the presence of dimethylallyl diphosphate to both geranyl diphosphate (GPP) and farnesyl diphosphate (FPP). These data suggested that, unlike the green peach aphid and the pea aphid, the cotton aphid appears to contain only a single IPPS with dual FPP/GPP synthase activity. (c) 2010 Elsevier Ltd. All rights reserved.