BOMBYXIN GENE-EXPRESSION IN TISSUES OTHER THAN BRAIN DETECTED BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION (RT-PCR) AND IN-SITU HYBRIDIZATION

Bombyxin is a 5 kDa insulin-related peptide produced in four pairs of medial neurosecretory cells in the brain of the silkmoth Bombyx mori. We demonstrate here the presence of bombyxin mRNA in tissues other tha n brain: ganglia, epidermis, testis, ovary, fat body, silk gland, Malp ighian tubule, midgut, and hindgut of the Bombyx fifth instar larvae. Bombyxin mRNA was detected by Oligotex reverse transcription-polymeras e chain reaction (RT-PCR), a rapid and simple procedure of reverse tra nscription-PCR, and in situ hybridization. The Oligotex RT-PCR method effectively eliminated the contaminating DNA in RNA samples and amplif ied bombyxin mRNA efficiently. In situ hybridization of the Bombyx ova ry clearly demonstrated the localization of the bombyxin mRNA in the o variole. The present study is the first demonstration of expression of brain neurosecretory peptide in tissues other than the central nervou s system in insects at RNA level.