CONTENS - International Organization of Plant Biosystematists

O 35
Evolution of a RNA polymerase gene family in the polyploid
Cerastium alpinum complex
Anne Krag Brysting
Centre for Ecological and Evolutionary Synthesis, Department of Biology, P.O.Box
1066 Blindern, N-0316 Oslo, Norway; a.k.brysting@bio.uio.no
The high-polyploid Cerastium alpinum complex (Caryophyllaceae) has been shaped
through repeated hybridization and polyploidization events. By the use of a network
algorithm and sequences of a single-copy nuclear region of the RNA polymerase II
gene family RPB2, we have previously shown that it is possible to untangle genome
mergings within this species complex. RPB2 nicely tracks the allopolyploid events
that gave rise to several recent (late Pleistocene) octo- and dodecaploid taxa.
However, only remnants of one or more earlier tetraploidization events are present as
pseudogenes in some of the supposed tetraploid ancestral taxa. Here, new data from
a non-coding region of the RNA polymerase IV gene family RPD2 is presented. In
some eudicot angiosperm taxa (e.g. Arabidopsis, Silene and Viola) this gene has
been independently duplicated. In some lineages subfunctionalization or
neofunctionalization of the two paralogues has occurred (probably specializing on the
two different RNA polymerase IV types existing in angiosperms), and in other
lineages one paralogue has become pseudogenised or completely lost. RPD2 is
duplicated also in Cerastium; two very different paralogues were amplified for all
analysed taxa, and for each of these paralogues several copies exist depending on
the ploidy level of the particular taxon. In the talk, I will present the most recent data
and in the light of results from other studies (Silene and Viola) discuss the fate of the
different paralogues following genome merging in the allopolyploid Cerastium
alpinum complex.
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