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

摘要

Comparison of the sequence and biological activity of ITP-related proteins from other insects on Schistocerca gregaria hindgut was carried out to provide further understanding of ITP interaction with its receptor (ITPR) and thus open new avenues ofinsect pest control if good ITPR antagonists can be developed. Using a specific bioassay (measurement of ileal Cl- transport) and Western blot analysis with antibodies raised to Schistocerca ion transport peptide (ScgITP) sequences, stimulatory ITP-related peptides were demonstrated in the corpora cardiaca (CC) of several orthopteran insects (Schistocerca gregaria, Locusta migratoria, Melanoplus sanguinipes, Xanthippus corallipes, Carausius morosus, Periplaneta americana and Acheta domesticus). ITP wasimmunologically detected in Schistocerca brain, the tissue in which ITP transcripts are found and which has some activity in the bioassay. Neither reciprocal bioassays nor immunological results reveal any differences between two locust species, Locusta and Schistocerca, which is consistent with cDNA analysis. Using Schistocerca-derived primers and the polymerase chain reaction (PCR), it was shown that Locusta brain contains RNA encoding for peptides with identical sequence to ScgITP and with only a single neutral amino acid change from Schistocerca ion transport-like peptide (ScgITP-L). Evidence is presented that ITP-L transcripts are present in at least 3 locust/grasshopper genera but it has not been possible to detect ITP-L peptide to date in any tissues assayed by Western blotting at a detection limit of 0.8 pmol/tissue. Results indicate high conservation of ITP structure and biological activity among these orthopteroids, in contrast to several other insect orders.