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SUMMARY:The Drosophila segmentation paradigm: A product of molecular co-op
 tion and the blind clock breaker? - Andrew Peel\, Institute of Molecular B
 iology and Biotechnology\, Crete
DTSTART:20120208T130000Z
DTEND:20120208T140000Z
UID:TALK35740@talks.cam.ac.uk
CONTACT:Matt Benton
DESCRIPTION:In Drosophila\, all body segments are patterned in the embryon
 ic blastoderm prior to gastrulation\, via the action of a cascade of mater
 nal\, gap\, pair-rule and segment-polarity genes. This textbook paradigm f
 or insect segmentation is evolutionary derived.  Ancestrally in insects\, 
 only anterior body segments were patterned in the blastoderm\, with poster
 ior (i.e. abdominal) segments forming after gastrulation\, in the context 
 of a cellularized and extending germband.  I have previously argued that t
 he evolution of the Drosophila segmentation paradigm required distinct evo
 lutionary transitions to occur at either pole of the egg (Peel\, 2008\; Pe
 el & Akam\, 2003): at the anterior pole\, the establishment of a secondary
  patterning centre as a prerequisite for an anterior shift in the embryoni
 c fate map within the egg\, and at the posterior pole\, the recruitment of
  gap genes to drive stripes of pair-rule gene expression that ancestrally 
 formed later\, sequentially\, and under the temporal control of an insect 
 segmentation clock\, similar to that operating in vertebrate somitogenesis
 .  I will present recent data from the emerging model beetle Tribolium cas
 taneum that support these evolutionary hypotheses:  In Tribolium\, materna
 l mRNAs are localized to the anterior pole in a microtubule dependent mann
 er\, similar to Drosophila\, despite the patterning of anterior (i.e. head
  and trunk) segments in the posterior half of the blastoderm. Secondly\, d
 uring the sequential formation of abdominal segments\, pair-rule gene homo
 logues oscillate in their expression\, with a two-segment periodicity\, su
 pporting their involvement in a Tribolium segmentation clock.  I will argu
 e that Tribolium might represent an intermediate stage in the evolution of
  the Drosophila segmentation paradigm\, and that recent data from this\, a
 s well as other holometabolous insects\, highlights the important role gen
 etic cooption has played in the evolution of developmental gene networks. 
LOCATION:Part II Lecture Theatre\, Department of Zoology
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