Regulation of cytochrome P-450 dependent steroid hydroxylase activity in Manduca sexta: Evidence for the involvement of a neuroendocrine-endocrine axis during larval-pupal development

Ecdysone 20-monooxygenase is the insect cytochrome P-450 dependent steroid hydroxylase system responsible for the conversion of ecdysone to 20-hydroxyecdysone. Using an in vitro radioassay, the levels of ecdysone 20-monooxygenase activity were quantified during embryogenesis in the egg, and in the fat body and midgut tissues during the fourth larval, fifth larval, and pupal-pharate adult stadia of the tobacco hornworm Manduca sexta. Although basal, ecdysone 20-monooxygenase activity was detected during the latter stages of larval embryogenesis. Postembryologically, a single major peak or increase was detected in both fat body and midgut tissues during each stadium. In the fourth larval instar, both fat body and midgut ecdysone 20-monooxygenase activities were found to peak in the latter half of the stadium at the time of spiracle apolysis; both activities dropped to basal levels by the time of ecdysis. During the fifth larval stadium, fat body steroid hydroxylase activity was found to rise during the feeding stage (days 1-4), then dropped back to basal levels by the onset of pharate pupal development on day 7 of the stadium. Midgut monoooxygenase activity during the fifth larval stadium, however, remained basal during the feeding stage, then rose dramatically to peak on day 5 with the onset of wandering, then dropped back to basal levels by the onset of pharate pupal development. Both fat body and midgut hydroxylase activities were basal during the pupal stage and only rose late in pharateadult development, just prior to adult eclosion. Arch. Insect Biochem. Physiol. 41:24-32, 1999.

Section: Introductionsupporting

confidence: 63%

Ecdysone 20‐monooxygenase activity during larval‐pupal‐adult development of the tobacco hornworm, Manduca sexta

Mitchell¹,

Crooks²,

Keogh³

et al. 1999

“…In accord with earlier studies (Smith et al, 1983;Keogh et al, 1989), in the present study the fat body and midgut monooxygenase activities during the fifth larval stadium were found to peak, respectively, on day 4 (Fig. 3) and day 5 (Fig.…”

Section: Discussionsupporting

confidence: 94%

“…Similar to earlier studies with M. sexta (Smith et al, 1983;Beckage and Templeton, 1986;Keogh et al, 1989) and several other insect species (see Smith, 1985;Halliday et al, 1986;Smith and Mitchell, 1986;Mitchell and Smith, 1988a;Chen et al, 1994), the ecdysone 20-monooxygenase activity in M. sexta fat body and midgut was found in the present study to fluctuate dramatically during postembryonic development (Figs. 1-6).…”

Section: Discussionsupporting

confidence: 90%

“…The fluctuations in ecdysone 20-monooxygenase activity suggest that this P-450 enzyme system is itself regulated, and numerous studies have reported modulation of ecdysone 20-monooxygenase activity by its substrate and product (see Smith, 1985;Lehmann and Koolman, 1986;Srivatsan et al, 1987;Agosin et al, 1988;Keogh et al, 1989;Williams et al, 1997), by a head factor released temporally coincident with PTTH (Smith, 1985;Keogh et al, 1989), by second messengers (i.e., cyclic AMP or cyclic GMP) and factors that influence or are part of second messenger based regulatory systems (Lehmann and Koolman, 1986;Hoggard and Rees, 1988;Hoggard et al, 1989;Keogh et al, 1991Keogh et al, , 1992Efuet et al, 1992), and by several diverse types of plant allelochemicals (Mitchell and Smith, 1988b;Mitchell et al, 1993Mitchell et al, , 1997.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Ecdysone 20-monooxygenase activity during larval-pupal-adult development of the tobacco hornworm,Manduca sexta

Mitchell

Crooks

Keogh

et al. 1999

Ecdysone 20‐monooxygenase is the insect cytochrome P‐450 dependent steroid hydroxylase system responsible for the conversion of ecdysone to 20‐hydroxyecdysone. Using an in vitro radioassay, the levels of ecdysone 20‐monooxygenase activity were quantified during embryogenesis in the egg, and in the fat body and midgut tissues during the fourth larval, fifth larval, and pupal‐pharate adult stadia of the tobacco hornworm Manduca sexta. Although basal, ecdysone 20‐monooxygenase activity was detected during the latter stages of larval embryogenesis. Postembryologically, a single major peak or increase was detected in both fat body and midgut tissues during each stadium. In the fourth larval instar, both fat body and midgut ecdysone 20‐monooxygenase activities were found to peak in the latter half of the stadium at the time of spiracle apolysis; both activities dropped to basal levels by the time of ecdysis. During the fifth larval stadium, fat body steroid hydroxylase activity was found to rise during the feeding stage (days 1–4), then dropped back to basal levels by the onset of pharate pupal development on day 7 of the stadium. Midgut monoooxygenase activity during the fifth larval stadium, however, remained basal during the feeding stage, then rose dramatically to peak on day 5 with the onset of wandering, then dropped back to basal levels by the onset of pharate pupal development. Both fat body and midgut hydroxylase activities were basal during the pupal stage and only rose late in pharate‐adult development, just prior to adult eclosion. Arch. Insect Biochem. Physiol. 41:24–32, 1999. © 1999 Wiley‐Liss, Inc.

“…9922), with properties of NADPH-requiring cytochrome P450 dependent steroid hydroxylases (Smith, 1985). In most insect species investigated so far, it was demonstrated that ecdysone 20-monooxygenase activity fluctuated dramatically during postembryonic development, suggesting that ecdysone 20-monooxygenase plays a crucial role in postembryonic development (Feyereisen and Durst, 1980;Smith, 1985;Smith and Mitchell, 1986;Keogh et al, 1989;Chen et al, 1994;Weirich et al, 1996). During embryonic development, however, very little is known regarding the biochemical characterization and developmental fluctuation of this enzyme system, even though the changes in the amount of 20-hydroxyecdysone have been demonstrated in several insect species (Gharib et al, 1981b;Hagedorn, 1985;Hoffmann and Lagueux, 1985;Sonobe et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Ecdysone 20-monooxygenase in eggs of the silkworm,Bombyx mori: Enzymatic properties and developmental changes

Horike

Sonobe

1999

Ecdysone 20‐monooxygenase in eggs of the silkworm Bombyx mori was characterized in relation to embryonic development. First, subcellular fractions were prepared by means of differential centrifugation, and analyzed using marker enzymes and antibodies against NADPH‐cytochrome P450 reductase. It was demonstrated that most ecdysone 20‐monooxygenase activity was associated with microsomes, and that there was little or no intrinsic mitochondrial ecdysone 20‐monooxygenase. Next, conditions for the measurement of ecdysone 20‐monooxygenase activity were established for the microsomal fraction, and changes in the enzyme activity were measured in diapause eggs and non‐diapause eggs during early embryogenesis. It was demonstrated that enzyme activity in diapause eggs remained at a low level, while that in the non‐diapause eggs increased from the gastrula stage. The increase in egg ecdysone 20‐monooxygenase activity was prevented by actinomycin D and α‐amanitin, suggesting that gene transcription is required for eliciting an increase in ecdysone 20‐monooxygenase activity. Arch. Insect Biochem. Physiol. 41:9–17, 1999. © 1999 Wiley‐Liss, Inc.