In Vivo and In Vitro Biosynthesis and Metabolism of Methyl Farnesoate, Juvenile Hormone Iii, and Juvenile Hormone Iii Acid in the Mosquito Aedes aegypti

Abstract

Biosynthesis and metabolism of juvenile hormone (JH) III in vivo and in vitro were studied in female Aedes aegypti (L.). [12-3H]Methyl farnesoate was used to follow the synthesis and [12-3H]-(10R)-JH III to study metabolism. The rate of biosynthesis of [12-3H]JH III in vivo after adult eclosion increased from 9 fmol/h per female at 1 h to 22 fmol/h per female at day 6. The rate of biosynthesis by exposed corpora allata (CA) in vitro was 23 fmol/h per CA during the 1st d after adult eclosion, then dropped to 4.8 fmol/h per CA on day 3, then increased again to a constant level of synthesis (12 fmol/h per CA) at days 4-6. Immediately after blood feeding, the rate of synthesis of [12-3H]JH III in vivo and in vitro increased to 27 fmol/h per female and to 23 fmol/h per CA, respectively. The rate of synthesis then decreased in vivo to 12 fmol/h per female at 4 h and in vitro to 6 fmol/h per CA 10 h after the blood meal. After this decrease, the rate of synthesis of [12-3H]JH III increased again reaching a peak of 25 fmol/h per female at 48-96 h in vivo and 12 fmol/h per CA at 72 h in vitro. These results indicated that the CA of sugar-fed and blood-fed female A. aegypti synthesized JH III in vivo and in vitro from [12-3H]methyl farnesoate. When [12-3H]-(10R)-JH III metabolism was followed in vivo in female A. aegypti, the ratio between JH III diol acid:JH III acid:JH III diol was 17:4:1, indicating that JH III was first hydrolyzed by JH III esterase to the acid form, then hydrated to the diol acid by JH III epoxide hydrase. Females treated with [12-3H]JH III acid converted 46% of the JH III acid in 60 min to the diol acid. These results indicated that the enzyme epoxide hydrase acted on JH III acid 17 times faster than JH III.

Nutritional regulation of JH synthesis: a mechanism to control reproductive maturation in mosquitoes?

“…After a female takes a blood meal, the JH level falls rapidly and reaches its lowest point 24 h after the blood meal (Shapiro et al, 1986). The dramatic decrease observed after blood ingestion primarily results from a decrease in the production of JH by the CA, increased degradation of JH by esterase activity, and its conversion to other hormone metabolites (Shapiro et al, 1986;Readio et al, 1988;Borovsky et al, 1992;Lassiter et al, 1994).…”

“…aegypti. Additional unidentified allatostatins showing inhibitory activity may exist and be responsible for regulating rates of JH biosynthesis during the gonotrophic cycle, especially after blood feeding (Shapiro et al, 1986;Borovsky et al, 1992;Li et al, 2003a).…”

The haemagglutination activity in the different developmental stages and changes of this activity caused by analogues of insect hormones in two members of the Culex pipiens complex of mosquitoes

“…Biosynthesis and degradation regulate the JH titres required for physiological events (Roe & Venkatesh, 1990). In adult mosquitoes, changes in the rate of Juvenile Hormone biosynthesis and release account partially for Juvenile Hormone regulation (Readio et al ., 1988; Borovsky et al ., 1992), whereas metabolism appears to play a complementary role in Juvenile Hormone reduction during the critical periods of reproductive development (Shapiro et al ., 1986; Borovsky et al ., 1992; Lassiter et al ., 1994). Little is known about the metabolism of Juvenile Hormone in preimaginal stages of mosquitoes and many other Holometabola.…”

Pathway and regulation of JHIII‐bisepoxide biosynthesis in adult Drosophila melanogaster corpus allatum

“…We have calculated (from chromatographic peak heights) that of the 20 pM MF used in the previous experiments, less than 2% conversion to JHB3 would have been easily discernable. Aedes aegypti CA synthesize JHIII from exogenous tritiated MF in vitro (Borovsky et al, 1992). The lack of synthesis of JHB3 from MF or JHIII is probably due to the absence of these pathways, and not due to lack of CA permeability.…”