The influence of juvenile hormone on polyploidy and vitellogenesis in the fat body of Locusta migratoria.

Abstract

Abstract Somatic polyploidy is a common developmental feature of endocrine target tissues, including vertebrate liver and insect fat body. Vitellogenin (Vg) synthesis in locust fat body is under strict control of juvenile hormone (JH) and is correlated with DNA synthesis and massive polyploidization of the tissue. We have used this system to concurrently monitor interactions between hormone, specific protein synthesis, and generation of cells with defined ploidy levels. Normal maturation of both males and females were compared, as were animals treated with precocene III and the JH analog ZR-515. Following are the main results and observations: Polyploidization occurs in both males and females but is much more pronounced in the latter. Peak DNA synthesis occurs in females just before onset of Vg synthesis and is coincident with predominant appearance of octoploid (8c) cells. In males DNA synthesis peaks earlier than in females, during transition from 2 c to 4 c cells, and then declines. Suppression of JH production by precocene prevents Vg synthesis completely and also inhibits DNA synthesis and generation of higher ploidy cells in both sexes. Reexposure of withdrawn animals to hormone reversed the foregoing conditions, but the disparity between sexes in timing of DNA synthesis and bulk tissue ploidy level was maintained. The developmental significance of these results is discussed.