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Full Abstracts – EVOLUTION AND QUANTITATIVE GENETICS I
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Molecular Evolutionary Analysis of Flightin Reveals a Novel Protein Motif unique to Pancrustacea.
Jim O. Vigoreaux
1
, Pedro Alvarez-Ortiz
1
, Felipe
Soto
1,2
. 1) Department of Biology, University of Vermont, Burlington, VT; 2) Illinois Natural History Survey, Champaign, IL.
Flightin is a thick filament protein that in Drosophila melanogaster is uniquely expressed in the indirect flight muscles (IFM). Flightin imparts rigidity and
structural stability to the thick filament and its expression is essential for flight. Given the importance of flight acquisition in the evolutionary history of
insects, here we study the distribution and phylogeny of flightin. Flightin has been identified in all hexapods (Collembola, Protura, Diplura and insect Orders
Thysanura, Dictyoptera, Orthoptera, Pthiraptera, Hemiptera, Coleoptera, Hymenoptera, Lepidoptera, Diptera) and crustaceans (Orders Anostraca, Cladocera,
Isopoda, Amphipoda, Decapoda) examined to date. The presence of flightin in Entognatha, the basal crustacean Daphnia, and derived insect and crustacean
orders suggest flightin is widespread in Pancrustacea. It is not present in chelicerates, myriapods, or any phyla outside Arthropoda suggesting flightin dates
back to the origin of extant Pancrustacea, ~600 MYA. Flightin is characterized by a well conserved sequence that is 52 amino acids long in hexapods and 48
to 56 amino acids in crustaceans. At least six sites are invariant, including an N-terminal tryptophan (W), two closely spaced tyrosines (Y), and a C-terminal
arginine (R). Our data suggest this sequence represents a novel motif, herein referred to as WYR, that is unique to flightin and paraflightin, a putative
flightin paralog detected only in decapods. Mosquitoes, sandflies and the amphipod (Gammarus) express two kinds of ESTs but only in the amphipod are the
isoform differences within WYR. Phylogenetic analysis suggests that paraflightin originated before the divergence of amphipods, isopods and decapods. In
summary, flightin evolved well before the appearance of flight in insects suggesting flightin was secondarily adapted for its flight muscle-specific function in
higher dipterans.