GOEHNER, Nicholas*; KELSTRUP, Hans; KVALHEIM, Lisa; ZUMWALT, Kari; EREZYILMAZ, Deniz; RIDDIFORD, Lynn; University of Washington; University of Washington; University of Washington; University of Washington; University of Washington; University of Washington: The Search for the Transcription Factor Broad in Non-Insectan Arthropods
In insects the ecdysone-regulated Broad transcription factor regulates morphogenetic changes at the molts. In the hemimetabolous, direct-developing insects such as the milkweed bug, Broad is first expressed in the embryo and is necessary for progressive morphogenesis of the wing pads and pigmentation during the nymphal molts. Broad then must disappear to allow transformation to the adult. By contrast, in insects with complete metamorphosis such as moths and flies, Broad is pupal-specific and is necessary for transformation of imaginal primordia into pupal structures. It also prevents premature adult differentiation. Using PCR primers for a portion of the conserved N-terminal Broad-Tramtrack-Bric-a-brac (BTB) domain, we have obtained putative Broad-encoding sequences from the direct-developing amphipod Apohyale pugetensis and the metamorphic barnacles Balanus nubilis and Balanus glandula. Two cDNA clones present in the lobster Homarus americana EST library show nearly 90% identity with the amphipod Broad sequence. Currently we are analyzing the developmental expression of Broad in these crustaceans to determine if this transcription factor is playing a similar metamorphic role as in insects. By contrast, no sequence highly similar to Broad was found in the pycnogonid Anoplodactylus iridintestinalis. Instead a PCR product encoding a bric-a-brac ortholog was found. Its role in the addition of pairs of limb bud at each of the 3rd-5th molts is under study. Thus, Broad appears to be important for metamorphosis of both insects and crustaceans, but its evolutionary origin is still a mystery. Supported by the Friday Harbor Laboratories Research Apprenticeship Program and by an REU supplement from NSF to LMR.