A genotype-phenotype association for autopolyploid meiosis stabilisation

Polyploidy occurs in all eukaryotic kingdoms, and is associated with adaptability, speciation and evolvability. At the same time, it is also one of the most dramatic mutations possible, often resulting in catastrophic problems during meiosis, when ensuring stable chromosome segregation and genome integrity is paramount. Because efficient meiosis is required for the formation of euploid gametes during sexual reproduction, selection acts strongly to optimize meiosis gene functions immediately upon the whole genome duplication that gives rise to polyploidy.In allopolyploids (formed by both genome duplication and interspecies hybridization), loci required for correct chromosome pairing have been identified in wheat, oil seed rape and Arabidopsis suecica. However, in autopolyploids (which form within-species, without hybridisation), there has been no functional confirmation of any gene controlling polyploid stabilization, although we have detected clear signatures of selection in eight meiotic genes (ASY1, ASY3, PDS5b, PRD3, REC8, SMC3, ZYP1a, ZYP1b) controlling chromosome pairing and the formation of the synaptonemal complex (SC) in the young autopolyploid Arabidopsis arenosa. The eight meiosis loci displaying highly differentiated alleles in A. arenosa were also reported in A. lyrata autotetraploids.In this study we PCR amplified coding regions of the eight meiosis genes from 52 A. arenosa and A. lyrata autotetraploids collected from different populations in Austria and Germany. Nextera LITE libraries were made from these amplicons, barcoded per plant and sequenced with by MiSeq. The proportion of diploid and highly differentiated tetraploid meiotic alleles per plant were determined by SNP frequency. This was then integrated with cytological analysis of meiotic metaphase I to determine what alleles modulate male meiotic recombination.