Ecdysteroids control vitellogenesis and egg maturation in pharate adult females of the Indianmeal moth, Plodia interpunctella

Abstract

(D. WB., V.J.B.) Vitellogenesis occurs during the late pharate adult stage in the lndianmeal moth, Plodia interpunctella. Repeated treatment of pharate adult females with doses of 20-hydroxyecdysone (20HE) from 10 to 250 ng per pupa suppressed oocyte growth and inhibited yolk protein accumulation in the oocytes. Treatment of the pharate adults with a biologically inactive ecdysteroid analogue, 22-isoecdysone, had no effect on egg maturation or yolk protein accumulation. The hormonal action of 20HE was not through the inhibition of the corpora allata or juvenile hormone levels, because treatment with a juvenile hormone analogue did not reverse the inhibition by 20HE treatment. Exposure of early vitellogenic ovaries to 20HE in organ cultures in vitro showed that 20HE had a direct effect on the ovarian synthesis of YP2. At 20HE concentrations below 10 nM, YP2 synthesis was minimal, at 10 nM 20HE YP2 synthesis was maximal, and at concentrations higher than 10 nM YP2 synthesis was suppressed to 35% of the maximal level. Synthesis of most other ovarian proteins remained constant with the changing 20HE concentrations. Ovarian RNA from treated females translated in a reticulocyte lysate demonstrated that the hormonal effect of 20HE on the ovarian tissues was on the specific accumulation of translatable YP2 transcript as well as transcripts for a few other polypeptides. This study shows that 20HE controls the rate of egg development during metamorphosis and that declining titers of 20HE regulate the expression of adult genes.

Dynamics of juvenile hormone-mediated gonadotropism in the lepidoptera

“…But it is the declining hemolymph ecdysteroid titer that triggers vitellogenin synthesis in fat bodies in the early pupal stage, ca. 83 h after the pupal molt; continued Vg synthesis and initiation of Vg incorporation into oocytes begins 96 h after pupation and these species complete egg maturation during late pupal stage under the influence of, as yet, other unidentified factors (Shirk et al, 1990(Shirk et al, , 1992. These authors demonstrated also that artificial reversal of the waning ecdysteroid titers blocked Vg sequestration by oocytes.…”

Vitellogenesis and Post-Vitellogenic Maturation of the Insect Ovarian Follicle

“…However, none of the other yolk protein subunits is detectable at this time. By culturing early vitellogenic ovaries in varying concentrations of 20E, it was shown that the continuation of YP2 synthesis requires low concentrations of 20E but is inhibited by high levels of the hormone (Shirk et al, 1990). These findings suggest that the action of the ecdysteroids is to regulate the progression of vitellogenesis by acting directly on the synthetic activity of the ovarian tissue.…”

“…However, Vn cannot be detected by immuno-gold staining with anti-YP1 or anti-YP3 antisera in the terminal follicles until after 112 h after pupation (Zimowska et al, 1994(Zimowska et al, , 1995. Repeated treatments of pharate adult female pupae with 20E leads to the suppression of the oocyte growth and yolk protein accumulation (Shirk et al, 1990), suggesting that the developmental progress of female P. interpunctella toward vitellogenesis is regulated by the declining titers of ecdysteroids.…”

“…The progress of the female toward the initiation of vitellogenesis is regulated by the declining levels of the ecdysteroids (Shirk et al, 1990). After final assembly by 36 h post-pupation, the follicles remain in a previtellogenic state until 92 h after pupation.…”

Biochemical Analyses of Action of Chlorfluazuron as Reproductive Inhibitor in Spodoptera litura

“…Therefore, these reductions were responsible for reduction in different parameters of spermatogenesis and testicular development reported by Perveen (2000b). Ecdysteroids control vitellogenesis and egg maturation in pharate adult females of the Indian meal moth, Plodia interpunctella (Hubner) (Shirk et al, 1990). They include ecdysone and 20-hydroxyecdysone, as well as hydrophilic conjugates of these and other ecdysteroids in both the silk moth, Bombyx mori Linnaeus (Ohnishi and Chami, 1977) and H. cecropia (Rubenstein et al, 1986).…”