Priming effect in gene activation by juvenile hormone in locust fat body

Abstract

When an active JH analog (methoprene or pyriproxyfen) is administered to JH‐deprived (precocene‐treated) adult female locusts, there is a delay of about 24 h before vitellogenin (Vg), the product of a JH‐dependent gene, is found in the hemolymph. If a dose of JH III or methoprene, itself too low to induce any detectable Vg, is administered 12–48 h before the inducing dose of JH analog, however, the appearance of Vg after the inducing treatment is accelerated by about 12 h. This effect is described as priming. It is proposed that priming involves the synthesis of a specific transcription factor for Vg and other JH‐dependent genes. A system suitable for testing this hypothesis is provided by transcription in locust fat body nuclear extracts, using G‐free cassettes as reporter sequences. Protein extracted from fat body of JH‐deficient (precocene‐treated) locusts transcribes from the control non‐specific AdML promoter but not from the promoters of the two JH target genes. Preparations from normal adult female fat body, or from that of locusts treated with precocene and later with a JH analog, on the other hand, transcribe from the promoters of the JH‐dependent Vg and jhp21 genes, as well as the AdML promoter. This demonstrates the JH‐induced appearance of a specific transcription factor. The cell‐free transcription system is suitable for further analysis of the molecular components of JH regulated transcription. © 1996 Wiley‐Liss, Inc.

Final steps in juvenile hormone biosynthesis in the desert locust, Schistocerca gregaria

“…JH has been reported to play multiple roles in the reproductive physiology of locusts. In females, it has been implicated in patency and induction of vitellogenin biosynthesis by the fat body (Sevala et al, 1995;Verlinden et al, 2009;Wyatt et al, 1996). In males, JH enhances spermatogenesis and pheromone biosynthesis and appears to be involved in the induction of yellow colouration of sexually mature crowded locusts (Jones, 1978;Pener, 1991;Tawfik et al, 2000;Wybrandt and Andersen, 2001).…”

Two hexameric cyanoprotein subunits from an insect, Riptortus clavatus

“…The activation of CPA expression after JHA treatment usually takes a few days, with some variation of time depending on the batch or nutritional condition of insects. Wyatt et al [52] have reported a 'priming' effect of JH for activation of Vg genes in the L. migratoria fat body. In their system, if the females are pre-treated with a priming dose of JH or JHA, which itself is too low to activate Vg genes, the lag time observed from the inducing dose of JHA until the detectable expression of Vg genes is shortened considerably.…”

Juvenile Hormone receptor Met is essential for ovarian maturation in the Desert Locust, Schistocerca gregaria

“…The role of JH as a master regulating gonadotropin in insect female reproduction is established in phylogenetically basal species, such as orthopterans (the insect order to which locusts belong), while ecdysteroids seem to have taken over this leading role in some lepidopteran and most dipteran species 3,4 . In female locusts, JH, synthesized in the corpora allata (CA, part of the retrocerebral complex), stimulates vitellogenin (Vg) production in the fat body by activating Vg gene transcription 5 . Furthermore, JH also binds to membrane receptor sites in the ovarian follicular epithelium to initiate events that cause cells to shrink 6–10 .…”