Influence of Pyriproxyfen on the Expression of Haemolymph Protein Genes in the Colorado Potato Beetle,Leptinotarsa decemlineata

Pyriproxyfen, a potent juvenile hormone analogue for the Colorado potato beetle, Leptinotarsa decemlineata, was applied topically to last-instar larvae and short-day adults at different times after moulting. The effect of the hormone analogue on concentration and composition of protein in the haemolymph was studied at different intervals after pyriproxyfen application. The hormone analogue had little effect on total protein concentration of the haemolymph, but affected protein composition. Diapause protein 1 was prevented from being synthesized if pyriproxyfen was applied before the gene was activated and disappeared from the haemolymph if applied after the gene had been expressed. It therefore inactivated the gene for diapause protein in both larvae and adults. Pyriproxyfen also induced appearance of vitellogenin at both stages, indicating induction of expression of the vitellogenin gene. It also affected the stability of mRNA for diapause protein. The analogue caused mRNA for diapause protein 1 to disappear untimely compared to controls in last-instar larvae and short-day adults. The response of adults to the JHA was much more pronounced than that of larvae, although the analogue had a strong biological effect on last-instar larvae because it prevented metamorphosis at low doses. Copyright 1997 Elsevier Science Ltd. All rights reserved     

High-molecular-weight serum proteins from Locusta migratoria: identification of a protein specifically binding juvenile hormone III

ABSTRACT. Tritiated 10,11-epoxyfarnesyl diazoacetate (EFDA), a photoaffinity label, can be covalently attached to the binding site of a JH-III-specific binding protein in the haemolymph of Locusta migratoria migratorioides (R & F). The specificity of the binding of EFDA to the binding protein is verified by displacement with excess unlabelled JH-III, and EFDA can be used to identify the binding protein in native pore-limiting gradient poly(acrylamide) gel electrophoresis (PAGE) and sodium dodecyl sulphate-PAGE. The native binding protein has a molecular weight of 575,000 and is composed of seemingly identical subunits of molecular weight 81,000.
Three other high-molecular weight serum proteins are identified by native PAGE: a lipophorin, composed of two kinds of apolipophorins, a larval storage protein and a cyanoprotein. The molecular weights and subunit structures of these proteins are investigated, but none of these other high-molecular weight proteins bind JH-III to an appreciable extent.     

Adult diapause in the Colorado potato beetle, Leptinotarsa decemlineata: effects of external factors on maintenance, termination and post-diapause development

ABSTRACT. This study tests the effects of temperature, water, food and photoperiod on breaking diapause and resumption of activity (emergence from the soil) in Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) diapausing under natural winter conditions or at constant temperatures in the laboratory. Behavioural and physiological criteria were used to characterize the various phases of diapause. Three successive phases are distinguished during hibernation: 'diapause development' or true diapause, a facultative 'post-diapause quiescence' and, finally, a transient phase of post-diapause development leading to emergence from the soil. Diapause development is completed within 3 months in the field and its duration depends on temperature. Although they are buried in the soil during this phase, beetles remain sensitive to photoperiod when artificially exposed to it. They do not emerge from the soil when exposed to higher temperatures. Thereafter, they stay in a quiescent state maintained by low temperature, low humidity or lack of food. The response to temperature changes during hibernation. In the soil, activity begins when soil temperature reaches 4–5C, but this temperature is too low to permit postdiapause development. The transient phase has a temperature threshold between 8 and 10C, whereas emergence from the soil occurs only when the temperature exceeds 11C. Post-diapause development is influenced strongly by temperature and humidity. After emergence, post-diapause development leads eventually to reproduction. Food is essential for reproduction after diapause whereas photoperiod plays no further role.