EXPRESSION OF THE ALLATOSTATIN GENE IN ENDOCRINE-CELLS OF THE COCKROACH MIDGUT

Cockroach allatostatins are neuropeptides that have been isolated from the brain of Diploptera punctata and shown to inhibit juvenile hormon e production by the corpora allata. Enzyme-linked immunoassay and immu nocytochemistry with antisera to two allatostatins, ASB2 (AYSYV-SEYKRL PVYNFGL-NH2) and ASAL (APSGAQRLYGFGL-NH2), revealed that allatostatins were located not only in the insect brain but also in several periphe ral tissues including the cockroach midgut and hindgut. Allatostatin-l ike immunoreactivity was found in nerve fibers of the stomatogastric n ervous system as well as in intrinsic endocrine cells of the midgut. M idgut extracts were shown to be biologically active in an allatostatin bioassay and to contain several allatostatin-like peptides, including the octadecapeptide ASB2, which was identified by mass spectrometry f ollowing HPLC purification. Reverse transcription of brain mRNA follow ed by PCR with degenerate oligonucleotides for ASB2 and ASAL yielded a 338-bp fragment of the allatostatin gene that encoded six allatostati ns. In situ hybridization with this probe confirmed that an allatostat in gene is expressed in intrinsic endocrine cells of the midgut. Rever se transcription of midgut mRNA followed by PCR and sequencing of the product revealed that the same gene is expressed in the midgut and in the brain. Allatostatins are thus an example of insect ''brain-gut pep tides'' and we suggest that their function may not be restricted to th e regulation of juvenile hormone production.