Juvenile hormone acid methyltransferase: A key regulatory enzyme for insect metamorphosis

Proceedings of the National Academy of Sciences of the United States of America - Tập 100 Số 21 - Trang 11986-11991 - 2003
Tetsuro Shinoda1, Kyo Itoyama1
1National Institute of Vegetable and Tea Science, National Agricultural Research Organization, Kusawa 360, Ano, Mie 514-2392, Japan.

Tóm tắt

Juvenile hormone (JH) acid methyltransferase (JHAMT) is an enzyme that converts JH acids or inactive precursors of JHs to active JHs at the final step of JH biosynthesis pathway in insects. By fluorescent mRNA differential display, we have cloned a cDNA encoding JHAMT from the corpora allata (CA) of the silkworm,Bombyx mori(BmJHAMT). TheBmJHAMTcDNA encodes an ORF of 278 aa with a calculated molecular mass of 32,544 Da. The predicted amino acid sequence contains a conservedS-adenosyl-l-methionine (SAM) binding motif found in the family of SAM-dependent methyltransferases. Purified N-terminal 6×His-tagged recombinant BmJHAMT protein expressed inEscherichia colicatalyzed conversion of farnesoic acid and JH acids I, II, and III to their cognate methyl esters in the presence of SAM, confirming that this cDNA encodes a functional JHAMT. Putative orthologs,DmJHAMTandAgJHAMT, were identified from the genome sequence of the fruit flyDrosophila melanogaster, and a malaria vector,Anopheles gambiae, respectively. Northern blot and quantitative RT-PCR analyses revealed that theBmJHAMTgene was expressed specifically in the CA throughout the third and fourth instar. At the beginning of the last (fifth) instar, the expression level ofBmJHAMTdeclined rapidly and became undetectable by day 4 and remained so until pupation. Correlation of theBmJHAMTgene expression and the JH biosynthetic activity in the CA suggests that the transcriptional suppression of theBmJHAMTgene is crucial for the termination of JH biosynthesis in the CA, which is a prerequisite for the initiation of metamorphosis.

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Proceedings of the National Academy of Sciences of the United States of America

Tập 100 Số 21

11986-11991

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