Regulation of vitellogenesis in the fall armyworm, Spodoptera frugiperda (Lepidoptera : Noctuidae)

Studies were undertaken to investigate vitellogenesis and its regulation in female adults of the fall armyworm, Spodoptera frugiperda. A single female -specific protein, likely to be the S. frugiperda vitellogenin (Vg), appear ed approximately 5 h after adult eclosion in the hemolymph of virgin female s. The concentration of the protein increased with age as sodium dodecyl su lfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed. A protein wit h the same relative molecular mass was also present in egg extracts, but ab sent from hemolymph samples from male moths. The relative molecular mass of the designated S. frugiperda Vg was determined as 164.5+/-2.5 kDa. Vitello genic oocytes became visible 36-48 h after emergence and egg deposition beg an on day 3 of adult life. Vg could not be detected in the hemolymph of fem ales decapitated directly after eclosion. When decapitated virgin females w ere injected with the JH-mimic methoprene (MP), the level of Vg was compara ble to that in non-decapitated moths, indicating that vitellogenesis in S. frugiperda depends on juvenile hormone (JH). However, the number of vitello genic oocytes was somewhat lower than in non-decapitated virgin females. In jection of 20-hydroxyecdysone (20E) promoted Vg production to a similar ext ent in decapitated female moths, but in contrast to methoprene injection, t reatment with 20E never resulted in the production of vitellogenic oocytes. In vitro cultivated ovaries of adult females dissected directly after eclo sion produced lower amounts of ecdysteroids than those isolated on day 1 af ter emergence. Our results suggest a crucial role for 20E in the induction of vitellogenesis in the noctuid S. frugiperda, while JH seems to be essent ial for the continued uptake of Vg by developing oocytes and may trigger 20 E biosynthesis in the ovary. (C) 2000 Elsevier Science Ltd. All rights rese rved.