Identification of biliverdin binding protein receptor and its regulation by juvenile hormone in the bean bug, Riptortus clavatus

1993 Fiscal Year Final Research Report Summary

• Project/Area Number: 04660047
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: 植物保護
• Research Institution: Mie University
• Principal Investigator: MIURA Ken Mie Univ, Faculty of Medicine, Assistant Prof., 医学部, 助手 (60219582)
• Co-Investigator(Kenkyū-buntansha): MATSOKA Hiroyuki Mie Univ, Faculty of Medicine, Associate Prof., 医学部, 講師 (10173816) ; ANDO Katsuhiko Mie Univ, Faculty of Medicine, Associate Prof., 医学部, 助教授 (90024710) ; CHINZEI Yasuo Mie Univ, Faculty of Medicine, Professor, 医学部, 教授 (60024709)
• Project Period (FY): 1992 – 1993
• Keywords: Biloverdin binding protein / Egg protein / Hemolymph protein / Receptor / Molecular biology

Research Abstract

Biliverdin binding protein, cyanoprotein (CP), which were found in the hemolymph (CP-1, 2, 3 and 4) and the egg yolk (CPegg) of the bean bug, Riptortus clavatus, were homo- and heterohexamer of two sorts of 76 kD subunit, CPalpha and CPbeta : CP-1 (identical to CPegg) = alpha_6 ; CP-2 = alpha_4beta_2 ; CP-3 = alpha_2beta_4 ; CP-4 = beta_6. cDNA cloning and and sequence analyzes of the two subunit established the sequence similarities among the CP subunits, other insect storage hexamers and arthropod hemocyanins. No similarities were found between the CP subunits and other biliverdin-binding proteins so far sequenced. Genomic DNA cloning was also done and demonstrated that both CPalpha and CPbeta genes were constructed by 11 exons. During nymphal development CP content and its synthetic activity fluctuated cyclically in accordance with each larval molt. Preferential sequestration of CP(mainly CP-4) by the fat body of the late fifth nymph was demonstrated by using ^<125>I-labeled CPs. Diapause adults synthesized CP at a low rate. In non-deapause adult females, CP-1 was synthesized throughout the reproductive stages, while no CP synthesis was found in males. CP-1 accumulated in the hemolymph of the reproductive females was sequestered bythe developing ovary and stored as CPegg. Selective sequestration of CP-1 by the ovary was confirmed by ^<125>I-labeled CPs. CP-4 (beta_6) was the main CP molecule in the diapause adults females, but in the postdiapause females induced by juvenile hormone (JH) treatment CP-4 (beta_6) synthesis was suppressed and, in turn, CP-1 (alpha_6) synthesis activated. Changes of CP mRNA content determined by northern blot analyzes were well coincident with the changes of the synthetic activity. This suggested that the expression of CP is regulated at the level of transcription and that JH induces a switching of a specific gene expression from CPbeta to CPalpha.