Molecular Mechanism of Juvenile Hormone Action

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Cyanoproteins of the bean bug, Riptortus clavatus, CP-1,2,3, and 4 are hexameric proteins composed of two different subunits, CPa and CPb. The cDNA libraries were constructed from poly (A) +RNA isolated from the fat body fromdiapause and diapause female adults. The cDNA clones encoding CPa and CPb were screened by using antisera against CPa and CPb, respectively. The nucleotide sequences of CPa and CPb cDNA inserts (a : 2217bp, b : 2163bp) predicted that CPa and CPb contain 693 and 686 residues, respectively. The identities at the level of amino acid sequence between the two CP subunits were calculated to be 68.0%. Homology search revealed that CPa and CPb were closely related to insect strage hexamers and arthropod hemocyanins. The author concluded that the hemocyanins of R.clavatus fall into the so-celled 'hexamerin' superfamily.The expression of Cyanoprotein (CP) was studied at the level of mRNA in the bean bug, Riptortus clavatus. Total RNA was extracted from the fat body of 5th nymphal stages, reproductive females and males, and juvenile hormone (JH) treated diapause females and males. The RNA was analyzed by northern blot analysis using cDNAs of CPa and CPb subunits as probes. The RND was also analyzed by in vitro translation. In the nymphs, both mRNAs appeared first on day-2 and then increased. CPa mRNA decreased to the molt while large amounts of CPb mRNA still remained at the end of the stage. In the reproductive females CPa expression was first detected on day-3 after emergence, then increased onward while no CPa mRNA was detected in the molts. As for CPb, a only trace expression was observed in the reproductive bugs. In the JH treatment to the diapause females resulted in the sift of CP expression from CPb to CPa while the treatment supressed completely the expression of both CPa and CPb in the diapause males.