Juvenile Hormone biosynthesis and release during oocyte development in Phormia regina Meigen

Abstract

AbstractA radiochemical assay for Juvenile Hormone (JH) biosynthesis and release by the corpus allatum (CA) was used to assess the effects of diet on CA activity of adult female Phormia regina (Meigen) fed either sugar‐water or sugar‐water‐liver. CC‐CA complexes were incubated in L‐methionine‐free medium 199 supplemented with 3H‐L‐methionine.The rate of JH release by the CC‐CA complexes is linear for 3 h and declines slightly thereafter. JH III appears to be one of the major components of the isooctane‐extractable product from incubated CC‐CA. High pressure liquid chromatographic analysis indicates that 10% of the released radiolabelled product is JH III. Rates of JH release show a strict dependence on L‐methionine concentration in the incubation medium, with optimal rates occurring between 100 and 150 μM L‐methionine. JH release is at a low level (<0.02pmolh‐1 per pair of CC‐CA) in flies fed only sugar‐water, but increases dramatically in flies fed sugar‐water‐liver (average release rate of 0.2pmolh‐1 per pair of CA, 24h after a liver meal). The rate of JH release increases steadily to more than 1.2pmolh‐1 per pair at 128h of age (i.e. 56h after a liver meal) at which time oocytes are mature. Elevated rates of JH release in vitro appear to be correlated in vivo with the appearance of vitellogenin in the haemolymph and its uptake by the developing oocytes.