Meiotic adaptation to allopolyploidy – MeioAdapt

Hybridization between related species resulting from allopolyploidy is ubiquitous in the evolutionary history of plants. From the outset, allopolyploid organisms face the challenge of proper chromosome segregation during meiosis in the presence of related, but non-identical chromosome sets (called homoeologues) inherited from the allopolyploid’s progenitors. Their fertility depends upon balanced chromosome segregation and thus upon formation of physical connections between homologous chromosomes via crossovers. The establishment of crossovers between homoeologous chromosomes however perturbs ordered chromosomal segregation, leading to the production of aneuploid gametes and reduced fertility. Meiotic stability in the allopolyploid context thus requires a tight control of meiotic recombination to prevent crossover formation between homoeologous chromosomes, while ensuring homologous crossovers. The existence of highly fertile natural allopolyploids shows that solutions exist and have arisen many times during evolution, but the mechanisms involved remain poorly understood. The MeioAdapt project aims at deciphering the processes underlying meiotic adaptation to allopolyploidy, and notably the molecular mechanisms that control pairing and recombination between homoeologous chromosomes.

Using the allotetraploid plant Arabidopsis suecica as a model and a combination of cutting-edge cytogenetic, genomic and epigenomic approaches, this research project will focus on three main objectives:

(1) Compare meiotic chromosome dynamics of natural A. suecica (highly fertile and genetically stable) and newly generated (synthetic) A. suecica plants that exhibit poor fertility and unstable meiosis. This analysis will reveal the mechanisms ensuring accurate homologous and homoeologous chromosome sorting during meiotic prophase I and the meiotic abnormalities responsible for reduced fertility of synthetic allopolyploids.

(2) Identify the factors controlling homoeologous pairing and recombination and characterize their roles during meiosis. A screen without a priori combined with a candidate-based approach should reveal the key regulators ensuring meiotic stability of evolved allopolyploids and the functions they fulfill.

(3) Elucidate how efficient control of homoeologous recombination is rapidly set up in the first generations following allopolyploidization. An in-depth analysis of meiosis across the early generations of synthetic A. suecica should identify the genetic and epigenetic mechanisms underlying meiotic adaptation of newly formed allopolyploids.

The MeioAdapt project will provide new and fundamental insights on the evolutionary processes enabling meiotic stabilization of allopolyploid organisms and notably shed new light on long-standing questions about meiotic adaptation to allopolyploidy. Elucidating the processes underlying genome stabilization and fertility is essential to comprehend success of allopolyploid species. It is hoped that MeioAdapt will contribute to improve plant breeding programs through knowledge transfer and consequently, participate in the production of innovative crop varieties.