Abstract
The biosynthesis and metabolism of ecdysteroids were compared in Drosophila larvae of the wild strain Canton-S and the thermosensitive mutant ecd1 at normal (22°C) and restrictive temperatures (29°C). At 22°C, ecdysteroid metabolism proceeds through a limited number of reactions: C-20 hydroxylation, C-26 hydroxylation followed by oxidation to ecdysonoic acids, C-3 oxidation, C-3 epimerization and conjugation. Epimerization and conjugation appeared to be minor pathways. The major processes of ecdysone conversion in Drosophila larvae were thus C-20 hydroxylation, a reaction that occurred in all types of larvae, and C-3 oxidation leading to the formation of 3-dehydroecdysone and 3-dehydro-20-hydroxyecdysone, a reaction particularly efficient in Dipteran larvae. Biosynthesis of ecdysteroids was investigated by [ 3H]chloresterol labelling. Active conversion into 20-hydroxyecdysone and 3-dehydro-20-hydroxyecdysone was observed. At restrictive temperature (29°C), while the wild strain Canton-S developed and normally pupated, the mutant ecd1 grew to full size but failed to pupate. The rate of ecdysteroid metabolism slowed down in the mutant, especially the conversion into 3-dehydrocompounds. Ecdysone biosynthesis fell dramatically in the mutant larvae but a basal level persisted and the conversion of chloresterol into 20-hydroxyecdysone and 3-dehydro-20-hydroxyecdysone was always observed.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call