Ecdysteroids during the third larval instar in I(3)ecd-1ts, a temperature-sensitive mutant of Drosophila melanogaster

Discrete pulses of molting hormone, 20‐hydroxyecdysone, during late larval development of Drosophila melanogaster: Correlations with changes in gene activity

“…Based on the additional analysis of separate populations of pre-wandering third instar larvae, this appears to also be the case in Drosophila. However, in contrast to the findings of Berreur et al (1984), little if any free E was detected in any of these early third instar extracts. Yet these repetitive, discrete elevations of 20E and 26E are the likely result of the increased secretion of E by the prothoracic gland cells of the ring gland, followed by its very rapid and efficient conversion to 20E by peripheral 20-hydroxylase (ecdysone 20-monooxygenase) activity (E20MO) (see Petryk et al, 2003) and/or to 26E by tissue 26-hydroxylase activity (Kayser et al, 1997;Williams et al, 2000) (Fig.…”

“…3). At these late stages of third instar development, i.e., just prior to pupation, ecdysteroids in larvae and pre-pupae are known to be primarily free 20E and E, along with both more polar and less polar metabolites (BelinskiDeutsch et al, 1983;Berreur et al, 1984). This differential response involving two antisera is analogous to that found during our identification of the true product of the prothoracic glands of many insects.…”

“…antibody preparations used previously (see Richards, 1981;Berreur et al, 1979Berreur et al, , 1984Schwartz et al, 1984). Nevertheless, both the H22 and SHO3 antisera exhibit similar affinity to 20E.…”

“…Nevertheless, past ecdysteroid titer data indicate to varying degrees the existence of one or more discrete small "peaks" of putative molting hormone activity prior to the final surge signaling metamorphosis to the pupa (see Richards, 1981;Berreur et al, 1984;Schwartz et al, 1984;Deak et al, 1988;Parvy et al, 2005;see Andres et al, 1993). These would perhaps be analogous to the so-called "commitment" peak(s) observed during the last larval stage of Lepidoptera (Bollenbacher et al, 1975;Riddiford, 1976;Wolfgang and Riddiford, 1986;Parlak et al, 1992;Dai et al, 1995).…”

“…Thus, it is not surprising that the published studies present ecdysteroid titers with different numbers and developmental timing (see Richards, 1981;Berreur et al, 1979Berreur et al, , 1984Schwartz et al, 1984;Parvy et al, 2005). The number, timing, and composition of low-amplitude elevations during the feeding stage of the last (third) larval instar are of importance because one or more may be analogous to the commitment peak of Lepidoptera (Bollenbacher et al, 1975;Riddiford, 1976;Wolfgang and Riddiford, 1986;Parlak et al, 1992;Dai et al, 1995).…”