During the five years of this project, we conducted a number of experiments that gave us novel insights into the evolution of polyploid meiosis, and helped establish Arabidopsis arenosa as an informative and useful model system for research in the immediate consequences of genome duplication, as well as the evolutionary response to these challenges. Moreover, this project opened important new research avenues in the biology of polyploids.
The main achievements of the project in its 60 months are:
1) One of the most important sets of experiments we performed was to establish in detail what specifically goes awry in neo-tetraploid meiosis immediately after genome duplication. Though there have been many cytological studies reported previously, it was not clear what the cause really was in any particular case. We used novel super-resolution microscopy and immunocytology, coupled with new kinds of analyses to unravel what exactly is the problem for neo-polyploids. We show that through evolving novel features to a process called crossover interference, which patterns crossovers in diploids, established polyploids can stabilize chromosome interactions and bias them towards interacting as pairs as they do in diploids, without affecting pairing preferences. Importantly, we show that this solution is effective also at higher ploidy. This work is important for helping contextualize the functional effects of genes we are studying. A manuscript describing this work is currently in minor revision for Current Biology, and should be published later in 2021 (Morgan, White et al., 2021).
2) Another important study showed that derived alleles of two meiotic proteins with evidence of selection in the tetraploid lineage do have important roles in stabilizing tetraploid meiosis (Morgan et al 2020, PNAS).
3) We also generated additional understanding of the population genetics of A. arenosa (Monnahan et al. 2019, Nature Ecology and Evolution), as well as a genetic map for Arabidopsis arenosa which will be published this year (2021).
4) Studying the evolutionary dynamics of the meiosis genes in A. arenosa we found that tetraploid derived alleles were largely selected from either de novo alleles or standing variants no longer present in diploids; some genes show evidence of having co-evolved (Bohutinska et al. 2021, Molecular Biology and Evolution).
5) A collaborative side project on crossover interference led to new insights and a new model for how this important process works (Morgan et al., 2021, Nature Communications).
6) We are currently generating protein biochemical data to test the idea that the derived alleles of meiotic proteins differ functionally from diploid alleles, and to understand how. This work is in progress and will result in one or two additional publications in 2022.
7) The main project generated, through a chance discovery, additional work on the plasticity of meiotic recombination to temperature and its effects on tetraploids (Lloyd et al 2018, Genetics; Weitz et al., 2021, Molecular Ecology).
8) The results from the project have triggered additional thinking and ideas for follow-up work. Some of these ideas were presented in related reviews (Bomblies, 2020, Proc Royal Soc B; Henderson and Bomblies 2021, Annu Rev Genet; Morgan et al 2017, Proc Royal Soc B).
The main project goals were achieved, with only minor deviations from the original proposal as results warranted.
