Key role of Met in the regulation of insect metamorphosis by JH

Metamorphosis of holometabolous insects such as beetles or butterflies is a marked change of form between juvenile and adult stages that enables the larva to efficiently utilize food sources and the flying adult to spread the species. Knowledge of metamorphosis is not only necessary for general understanding of development, but also for effective control of insect pests. The entry to metamorphosis depends on the morphogenesis-promoting ecdysteroids and the antagonistically acting juvenile hormone (JH). JH has been known to prevent metamorphosis since the work of V.B. Wigglesworth (1934). However, the mechanism of JH action has remained an enigma as neither a JH receptor nor its signaling pathway are known. By using the red flour beetle Tribolium castaneum, we showed that a gene Methoprene-tolerant (Met), originally uncovered as a mutation conferring resistance to JH in the fly Drosophila, mediates the anti-metamorphic JH effect. Loss of Met function renders Tribolium insensitive to JH and, unlike in Drosophila, it also causes the beetle larvae to metamorphose precociously. In response to JH, Met controls metamorphosis by regulating expression of the Broad-Complex gene, which is required for the metamorphic changes. Our latest studies (Konopova & Jindra 2007, 2008) for the first time demonstrate the key role of Met in the regulation of insect metamorphosis by JH and thus support the disputed function of Met as a receptor or transducer of the JH signal.

Konopova, B., Jindra, M.: Juvenile hormone resistance gene Methoprene-tolerant controls entry into metamorphosis in the beetle Tribolium castaneum. - Proc. Natl. Acad. Sci. USA,104: 10488-10493 (2007)