Meeting Abstract

56.4  Saturday, Jan. 5  Endocrine and developmental basis for the evolution of the pupa in holometabolous insects. SUZUKI, Y.**; TRUMAN, J.W.; RIDDIFORD, L.M.; University of Washington, Seattle; University of Washington, Seattle; University of Washington, Seattle ysuzuki2@u.washington.edu

The evolutionary basis of metamorphosis in holometabolous insects has attracted considerable attention. Yet the developmental and evolutionary origin of the pupa remains an enigma. One key gene expressed during metamorphosis is the transcription factor, Broad (Br). In the flour beetle Tribolium castaneum, there are 5 isoforms of br, each with a common core region and a different zinc finger domain. When double-stranded RNA for the br core region was injected into a penultimate instar larva, an individual with primarily larval and adult characteristics was formed at the normal metamorphic pupal molt. Use of RNAi for the different isoforms individually and in combination showed that all but the Z5 isoform were important in specifying pupal morphogenesis. Our results suggest that the br isoforms 1) act to suppress adult differentiation and redirect development to form a stationary pupa, 2) regulate allometric growth of wings, and 3) regulate neuronal morphogenesis. We propose that the ecologically adaptive specialized morphology of the modern holometabolus insect pupa arose from a mobile nymph-like ancestor through co-option of Br expression. Supported by NIH GM060122.