Ligand regulation of juvenile hormone binding protein mRNA in mutant Manduca sexta

Insect hemolymph juvenile hormone binding protein (hJHBP) regulates periphe ral titers of its ligands, the juvenile hormones. In larvae of the black (b l) strain of the tobacco hornworm, Manduca sexta, treatment with small dose s of juvenile hormone I (JH I) can also regulate titers of hJHBP. To furthe r investigate this regulation, responsiveness of hJHBP mRNA expression to J H I was characterized in vivo. RNA analyzes revealed that transcript levels in fat body, the site of hJHBP synthesis, increased fivefold within severa l hours of treatment with physiological doses of hormone and remained eleva ted for approximately 16 h. Sensitivity to JH treatment was found to vary t emporally. To ensure transcript identity, a wild-type cDNA clone and a bl R T-PCR fragment were sequenced and found to be 99% homologous. Together, the se results suggest that JH participates in regulating expression of its tra nsport protein in bl larvae by modifying the in vivo abundance of hJHBP's m RNA transcript. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.