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SUMMARY:Adaptive evolution of meiosis in response to whole genome duplicat
 ion and habitat - Kirsten Bomblies\, Harvard University
DTSTART:20151001T120000Z
DTEND:20151001T130000Z
UID:TALK61119@talks.cam.ac.uk
CONTACT:38889
DESCRIPTION:Meiosis is essential for fertility of sexual eukaryotes and it
 s core structures and progression are conserved across kingdoms. Neverthel
 ess\, meiotic proteins are often less conserved in primary sequence than w
 e might expect\, and sometimes show evidence of having experienced directi
 onal selection. Why? What challenges does meiosis face that might cause it
  to evolve adaptively and how does this alter the system? Evidence from a 
 range of studies shows that two important factors can challenge the stabil
 ity of meiosis and drive evolutionary responses: whole genome duplication 
 and environmental factors\, especially temperature. Our group seeks to und
 erstand how meiosis evolves in response to challenges\, that is\, what its
  evolutionary plasticity is within the constraints of being an essential a
 nd complex structural progression. We use Arabidopsis arenosa\, which occu
 rs naturally as an autotetraploid and a diploid\, and where both cytotypes
  have colonized a range of habitats. In a genome scan for adaptation to wh
 ole genome duplication\, we found that eight interacting meiotic proteins 
 critical for axis formation and synapsis show strong evidence of having be
 en under selection in the tetraploid arenosas. This is associated with a r
 eduction in crossover number\, and a greater tendency for terminal localiz
 ation of chiasmata. More recently\, we found that two of the same genes un
 der selection in tetraploids\, also show strong evidence of having been un
 der selection in a diploid A. arenosa lineage. This lineage colonized a wa
 rmer lowland habitat (the ancestral form is found in cooler mountain envir
 onments)\, and we have evidence that this lineage evolved greater temperat
 ure tolerance of meiosis. Distinct alleles of the same genes were under se
 lection after both whole genome duplication and habitat colonization\, and
  thus have twice come under selection for apparently distinct reasons\; do
 es this suggest evolutionary constraint on the system? Does it indicate th
 at the same processes are challenged by distinct stresses? \nThe finding t
 hat the genes that came under selection in both lineages are known to inte
 ract also highlights the possible need for co-evolution of interacting par
 tners in meiotic evolution\, which may be more broadly relevant to the evo
 lution of proteins that participate in large complexes.\n
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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