Characterizing the function of Methoprene tolerant and its downstream genes in termites

Caste differentiation is one of the defining characteristics of eusocial animals. In social insects, caste transition is primarily regulated by juvenile hormone (JH). Yet, little is known about the genes and gene networks mediating JH signaling associated with caste differentiation.  Methoprene tolerant (Met), a putative insect JH receptor, and its downstream factor, Kruppel homolog 1 (Kr-h1) have been demonstrated to mediate JH action during development and reproduction in insects. Therefore it is likely that these factors also regulate JH action during caste development in social insects. We characterized molecular properties and function of a Met ortholog (RfMet) in the eastern subterranean termite, Reticulitermes flavipes. We analyzed developmental expression profile of the RfMet and the kruppel homolog-1  (RfKr-h1) during the JH-dependent soldier caste differentiation by the worker caste.  We show that silencing of RfMet redered R.flavipes resistance to the effects of ectopic JH, and suppressed the worker to soldier caste transition.  Molecular characterization in combination with RNAi experiments suggested that RfMet and RfKr-h1 are JH-responsive factors mediating JH action in termite caste differentiation.