Two juvenile hormone suppressible storage proteins may play different roles in Hyphantria cunea Drury.

ABSTRACT

We isolated and sequenced cDNA clones corresponding to two storage proteins (HcSP-1 and HcSP-2) from fall webworm, Hyphantria cunea. The cDNAs for HcSP-1 (2,337 bp) and HcSP-2 (2,572 bp) code for 753 and 747 residue proteins with predicted molecular masses of 88.3 and 88.5 kDa, respectively. The calculated isoelectric points are pI = 8.4 (HcSP-1) and 7.6 (HcSP-2). Multiple alignment analysis of the amino acid sequence revealed that HcSP-1 is most similar to SL-1 from S. litura (73.8% identity) and other methionine-rich hexamers, whereas HcSP-2 is most similar to the SL-2 alpha subunit from S. litura (74.8% identity) and other moderately methionine-rich hexamers. The two storage proteins from H. cunea shared only 38.4% identity with one another. According to both phylogenetic analyses and the criteria of amino acid composition, HcSP-1 belongs to the subfamily of Met-rich storage proteins (6% methionine, 10% aromatic amino acid), and HcSP-2 belongs to the subfamily of moderately methionine-rich storage proteins (3.2% methionine, 12.9% aromatic amino acid). Topical application of the JH analog, methoprene, after head ligation of larvae, suppressed transcription of the SP genes, indicating hormonal effects at the transcriptional level. The HcSP-1 transcript was detected by Northern blot analysis in Malpighian tubule, testis, and ovary, in addition to fat body where it was most abundant. The HcSP-2 transcript was detected only in fat body and Malpighian tubule. The accumulation of HcSP-1 in ovary and HcSP-2 in Malpighian tubule might be related to differential functions in both organs.