Premium
Location of ecdysteroid 22‐ O ‐acyltransferase in the larvae of Heliothis virescens
Author(s) -
Kubo I.,
Zhang M.,
Boer G.,
Uchima K.
Publication year - 1994
Publication title -
entomologia experimentalis et applicata
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 83
eISSN - 1570-7458
pISSN - 0013-8703
DOI - 10.1111/j.1570-7458.1994.tb00755.x
Subject(s) - ecdysteroid , heliothis virescens , ecdysone , biology , midgut , 20 hydroxyecdysone , biochemistry , brush border , insect , medicine , hormone , larva , botany , noctuidae , membrane , vesicle
Larvae of the tobacco budworm, Heliothis virescens , are resistant to high levels of ingested 20‐hydroxyecdysone which could cause potential inhibition to the development of many other lepidopteran species. This resistance is attributed to the ability of the larvae to metabolize this molting hormone to its 22‐acyl ester forms. When tobacco budworm larvae were fed large quantities of 20‐hydroxyecdyone, the hormonal metabolites were found in gut and fat body tissues. When incubated with 20‐hydroxyecdysone gut tissue converted 20‐hydroxyecdysone into its 22‐acyl ester metabolites. Lumen site of the midgut was found to be the major location of this bio‐transformation. In contrast, fat body tissue failed to convert 20‐hydroxyecdysone to 22‐acyl ester metabolites in vitro. After the oral injection of 3 H‐ecdysone, the major metabolites formed were ecdysone 22‐acyl esters whereas the majority of 3 H‐ecdysone was transformed to polar metabolites after it was injected into the hemocoel of the larvae. Similar distributions of ecdysteroid 22‐ O ‐acyltransferase and alkaline phosphatase activity in subcellular fractions demonstrates the co‐localization of these enzymes in plasma membrane of the gut epithelial cells. These results suggest that gut brush border membrane is the major site of ecdysteroid 22‐acyl ester formation in H. virescens larvae.