METHIONINE-RICH HEXAMERIN AND ARYLPHORIN AS PRECURSOR RESERVOIRS FOR REPRODUCTION AND METAMORPHOSIS IN FEMALE LUNA MOTHS

The storage proteins of Lepidoptera include a pair of methionine-rich hexamerins (MtH) that are more abundant in female pupae than in males. Their inferred support of female reproduction could be achieved eithe r by enhancing general pools of amino acids, or by hydrolyzing MtH at times and/or sites that direct its constituents to the synthesis of eg g proteins. The two models were tested in Actias luna, a saturniid mot h that makes its eggs during adult development. MtH and arylphorin (Ar H), the third major storage protein of this species, were labeled meta bolically with [S-35]-methionine and [H-3]-leucine, and injected indiv idually into wandering stage caterpillars. Isotope distributions at ec losion indicated that both hexamerins supported egg formation as well as adult tissue protein synthesis. In the absence of evidence for targ eting, MtH appears to support egg formation in A. luna by enhancing th e amino acid pools derived from ArH. Analysis of S-35 labeling and of S-35/H-3 ratios indicated, however, that ArH is consumed over a period that extends somewhat later in adult development than MtH. Difference s in timing should prove to be much greater in Lepidoptera that delay egg formation until after eclosion. (C) 1996 Wiley-Liss, Inc.