Discrete pulses of molting hormone, 20-hydroxyecdysone, during late larval development of Drosophila melanogaster: correlations with changes in gene activity.
Periodic pulses of the insect steroid molting hormone 20-hydroxyecdysone (20E), acting via its nuclear receptor complex (EcR/USP), control gene expression at many stages throughout Drosophila development. However, during the last larval instar of some lepidopteran insects, subtle changes in titers of ecdysteroids have been documented, including the so-called "commitment peak." This small elevation of 20E reprograms the larva for metamorphosis to the pupa. Similar periods of ecdysteroid immunoreactivity have been observed during the last larval instar of Drosophila. However, due to low amplitude and short duration, along with small body size and staging difficulties, their timing and ecdysteroid composition have remained uncertain. Employing a rigorous regimen of Drosophila culture and a salivary gland reporter gene, Sgs3-GFP, we used RP-HPLC and differential ecdysteroid RIA analysis to determine whole body titers of 20E during the last larval instar. Three small peaks of 20E were observed at 8, 20, and 28 hr following ecdysis, prior to the well-characterized large peak around the time of pupariation. The possible regulation of 20E levels by biosynthetic P450 enzymes and the roles of these early peaks in coordinating gene expression and late larval development are discussed.
Warren
James T
JT
Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA.
Yerushalmi
Yoram
Y
Shimell
Mary Jane
MJ
O'Connor
Michael B
MB
Restifo
Linda L
LL
Gilbert
Lawrence I
LI
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D004440:Ecdysone / Q000096:biosynthesis* / Q000737:chemistry; D004441:Ecdysterone / Q000096:biosynthesis* / Q000737:chemistry; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D007814:Larva / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D015394:Molecular Structure; D011863:Radioimmunoassay; D013997:Time Factors
D029721:Drosophila Proteins; D004440:Ecdysone; D004441:Ecdysterone; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C496261:Phm protein, Drosophila; C416219:DIB protein, Drosophila