cDNA and characterization of a specific peptide produced throughout adult diapause in the leaf beetle, Gastrophysa atrocyanea

H. Tanaka 1 , K. Sato 2 & K. Suzuki 1

1 Dept. of Bioscience and Technology, Faculty of Agriculture, Iwate University, Ueda 3-18-8, Morioka 020-8550, Japan; 2 Iwate Biotechnology Research Center, Narita 22-174-4, Kitakami 024-0003, Japan

The amino acid sequence has been determined for specific peptide produced throughout adult diapause in the leaf beetle, Gastrophysa atrocyanea (Tanaka et al., 1998). This peptide is cysteine-rich and has no homology with known proteins. In an attempt to analyze the physiological role of the diapause-specific peptide, we decided cDNA sequence of the peptide by RACE (358 bp) that includes the leader peptide (23 amino acid residues) and mature peptide (41 amino acid residues). It was found that the peptide mRNA is highly expressed in the fat body being the major source of this secretary peptide in the diapausing adult. By reason that the distribution of cysteine residues and their sequence motif are similar to conotoxins, we examined Ca 2+ channel-blocking activity in primary culture of mouse nerve cells, but the peptide did not inhibit Ca 2+ influx. On the other hand, we found an interesting alignment between the diapause-specific peptide and the polypeptides encoded in some insect baculovirus according to computer search (BLAST and FASTA). We also determined a disulfide bound within 6 cysteine residues. These results do not lead to the understanding of diapause mechanism in adult insects, but cDNA sequence of the diapause-specific peptide will be available to analyze the regulation of gene expression involved with diapause, and co-evolutional relation with the insect and baculovirus.

Index terms: cysteine-rich, conotoxin, baculovirus

More Topics on the Wing

About Us