Meeting Abstract
The developmental and genetic mechanisms underlying phenotypic plasticity and their contribution to evolution are of major interests to biologists. We are investigating the role of the insulin signaling pathway, known to link nutrition to growth in a wide range of organisms, in the ontogeny and evolution of polyphenic development in the beetle Onthophagus taurus. In this species males exhibit a nutrition-sensitive male dimorphism in which high nutrition results in fully horned fighter males, whereas development under low nutrition conditions result in hornless sneaker males. Using RNA interference-mediated gene knockdown we are investigating the role of two cardinal components of the insulin signaling pathway, the insulin receptor (which promotes cell proliferation when activated by insulin in the presence of high nutrition), and FOXO (a growth inhibitor downstream of the insulin receptor which is activated during nutrient stress). Results to date suggest that knockdown phenotypes of either gene depend strongly on the developmental timing of knockdowns. Phenotypes range from no effect to differential – and in part substantial – alterations of appendage size, and in particular decreased as well as increased horn growth relative to body size. Taken together, our results suggest that the insulin signaling pathway plays a key role in the regulating nutrition-dependent growth and horn polyphenism in Onthophagus taurus and possible many other taxa.
