Storage hexamer utilization in Manduca sexta

In preparing for metamorphosis insects store in their hemolymph and fat bodies a major nutrient reserve of 500-kDa hexamerins. At least three hexamerins serve this function in Lepidoptera, including arylphorin (ArH) and two high methionine proteins (M-MtH and V-MtH). Six day-old adults of Manduca sexta are shown here to have consumed over 99% of their pupal reserves of ArH and in the case of males, 99.8% of M- and V-MtH. In support of egg formation, however, females at this stage retain over 25% of their pupal reserves of the high methionine proteins. Demonstrated here are three factors contributing to the methionine protein reserves in day-6 adult females. (1) Pupal stores of the methionine proteins average 1.67 times larger in females than in males. (2) A fraction of this pupal store remains undiminished during pharate adult development: centrifugation of homogenates partitions the hexamerins into a fraction that is soluble in PBS and a smaller, particle-associated fraction that is not. Pharate adults consume most of the soluble fraction and relatively little of the particulate fraction, which then constitutes over half of the methionine protein reserves of post-eclosion females. (3) Both soluble and particle-associated reserves double in the week following eclosion and this suggests that adult females may resume the synthesis of V- and M-MtH. Though differing in amino acid sequence and antigenic properties, V-MtH and M-MtH showed no significant differences in their storage and utilization profiles.