Biology Reference
In-Depth Information
A
CA
PG
PG
CC
CC
Brain lobe
Brain lobe
20-Hydroxyecdysone
a
B
Head
eversion
Pupariation
Wandering
“Glue genes” induction
“Critical weight”
Day 0
Day 1
Day 2
Day 3
Day 5
Day 9
t
Embryo
L1
L2
L3
PP
Pupa
Adult
Figure 2.2 Ecdysone directs developmental transitions in Drosophila. (A) Ecdysteroids
are produced inprothoracic gland cells of the ringgland, which is attached to the anterior
side of the brain. Hormones are then released into the hemolymph and subsequently
converted to the biologically active form20-hydroxyecdysone (20E) in peripheral tissues.
(B) Schematic representation of whole-body concentrations of 20E during Drosophila
development. Three minor ecdysone pulses occur during the third instar and have been
suggested to trigger the physiological and behavioral changes indicated by the arrows.
PG, prothoracic gland; CA, corpus allatum; CC, corpora cardiaca; L1/L2/L3, first/second/
third instar; PP, prepupa.
Gilbert et al., 2002
). The conversion from cholesterol to ecdysone starts with
Neverland, a Rieske electron oxygenase, which generates 7-dehydrocholesterol
(
Yoshiyama, Namiki, Mita, Kataoka, & Niwa, 2006; Yoshiyama-Yanagawa
et al., 2011
). The last four steps toward 20E are also characterized and are carried
out by the cytochrome P450 enzymes Phantom, Disembodied, Shadow, and
