Molecular and functional characterization of a juvenile hormone acid methyltransferase expressed in the corpora allata of mosquitoes

• Published in: Insect biochemistry and molecular biology Vol. 39; no. 1; pp. 31 - 37
• Main Authors: Mayoral, Jaime G., Nouzova, Marcela, Yoshiyama, Michiyo, Shinoda, Tetsuro, Hernandez-Martinez, Salvador, Dolghih, Elena, Turjanski, Adrian G., Roitberg, Adrian E., Priestap, Horacio, Perez, Mario, Mackenzie, Lucy, Li, Yiping, Noriega, Fernando G.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-01-2009
• Subjects: Aedes aegypti; Amino Acid Sequence; amino acid sequences; Animals; biosynthesis; Bombyx mori; Cloning, Molecular; complementary DNA; corpora allata; Corpora Allata - chemistry; Corpora Allata - enzymology; Corpora Allata - growth & development; Culicidae - chemistry; Culicidae - enzymology; Culicidae - genetics; Culicidae - growth & development; developmental stages; enzyme activity; Farnesoic acid; Female; Gene Expression; Insect Proteins - chemistry; Insect Proteins - genetics; Insect Proteins - metabolism; Juvenile hormone; juvenile hormone biosynthesis; juvenile hormones; Juvenile Hormones - metabolism; messenger RNA; methyl farnesoate; Methyltransferase; methyltransferases; Methyltransferases - chemistry; Methyltransferases - genetics; Methyltransferases - metabolism; Molecular Sequence Data; Mosquito; nutritional status; recombinant proteins; Sequence Alignment; sequence homology; Aedes aegypti; Farnesoic acid; Mosquito; Methyltransferase; Juvenile hormone
• ISSN: 0965-1748; 1879-0240
• DOI: 10.1016/j.ibmb.2008.09.010

A juvenile hormone acid methyltransferase (JHAMT) was isolated as an abundant EST in a library of the corpora allata of the adult female mosquito
Aedes aegypti. Its full length cDNA encodes a 278-aa protein that has 43% amino acid identity with
BmJHAMT, a juvenile hormone acid methyltransferase previously cloned from
Bombyx mori. Heterologous expression produced a recombinant protein that metabolizes farnesoic acid (FA) into methyl farnesoate, as well as juvenile hormone acid into juvenile hormone III (JH III) with exquisite stereo specificity. Real time PCR experiments showed that JHAMT mRNA levels are not an unequivocal indicator of JH III synthesis rates; the
A. aegypti JHAMT gene, silent in female pupae, was transcriptionally activated just 4–6
h before adult eclosion. Radiochemical methyltransferase assays using active and inactive corpora allata glands (CA) dissected from sugar and blood-fed females respectively, clearly indicated that significant levels of JHAMT enzymatic activity are present when the CA shows very low spontaneous rates of JH III synthesis. Having the last enzymes of the JH synthetic pathway readily available all the time might be critical for the adult female mosquito to sustain rapid dynamic changes in JH III synthesis in response to nutritional changes or peripheral influences, such as mating or feeding. These results suggest that this gene has different roles in the regulation of JH synthesis in pupal and adult female mosquitoes, and support the hypothesis that the rate-limiting steps in JH III synthesis in adult female mosquitoes are located before entrance of FA into the synthetic pathway.