Occurrence of ion transport peptide (ITP) and ion transport-like peptide (ITP-L) in orthopteroids

Comparison of the sequence and biological activity of ITP-related proteins from other insects on Schistocerca hindgut will provide further understandi ng of ITP interaction with its receptor (ITPR) and may thus open new avenue s of insect pest control if good ITPR antagonists can be developed. Using a specific bioassay (measurement of ileal CT transport) and Western blot ana lysis with antibodies raised to Schistocerca ion transport peptide (ScgITP) sequences, we demonstrate stimulatory ITP-related peptides in the corpora cardiaca (CC) of several othopteran insects (Schistocerca gregaria, Locusta migratoria, Melanoplus sanguinipes, Xanthippus corallipes, Carausius moros us, Periplaneta americana and Acheta domesticus.). For the first time, we h ave immunologically detected ITP in Sehistocerca brain, the tissue in which ITP transcripts are found and which has some activity in the bioassay. Nei ther reciprocal bioassays nor immunological results reveal any differences between two locust species, Locusta and Schistocerca, which is consistent w ith cDNA analysis. Using Schistocerca-derived primers and the polymerase ch ain reaction (PCR), we show that Locusta brain contains RNA encoding for pe ptides with identical sequence to ScgITP and with only a single neutral ami no acid change from Schistocerca ion transport-like peptide (ScgITP-L). We present evidence that ITP-L transcripts are present in at least 3 locust/gr asshopper genera but have been unable to detect ITP-L peptide to date in an y tissues assayed by Western blotting at a detection limit of 0.8 pmol/tiss ue. Results indicate high conservation of ITP structure and biological acti vity among these orthopteroids, in contrast to several other insect orders. (C) 1999 Wiley-Liss, Inc.