Learning to tango with four (or more): the molecular basis of adaptation to polyploid meiosis.

Polyploidy, which arises from genome duplication, has occurred throughout the history of eukaryotes, though it is especially common in plants. The resulting increased size, heterozygosity, and complexity of the genome can be an evolutionary opportunity, facilitating diversification, adaptation and the evolution of functional novelty. On the other hand, when they first arise, polyploids face a number of challenges, one of the biggest being the meiotic pairing, recombination and segregation of the suddenly more than two copies of each chromosome, which can limit their fertility. Both for developing polyploidy as a crop improvement tool (which holds great promise due to the high and lasting multi-stress resilience of polyploids), as well as for our basic understanding of meiosis and plant evolution, we need to know both the specific nature of the challenges polyploids face, as well as how they can be overcome in evolution. In recent years there has been a dramatic uptick in our understanding of the molecular basis of polyploid adaptations to meiotic challenges, and that is the focus of this review.