Genomic and Meiotic Changes Accompanying Polyploidization

Hybridization and polyploidy have been considered as significant evolutionary forces in adaptation and speciation, especially among plants. Interspecific gene flow generates novel genetic variants adaptable to different environments, but it is also a gene introgression mechanism in crops to increase their agronomical yield. An estimate of 9% of interspecific hybridization has been reported although the frequency varies among taxa. Homoploid hybrid speciation is rare compared to allopolyploidy. Chromosome doubling after hybridization is the result of cellular defects produced mainly during meiosis. Unreduced gametes, which are formed at an average frequency of 2.52% across species, are the result of altered spindle organization or orientation, disturbed kinetochore functioning, abnormal cytokinesis, or loss of any meiotic division. Meiotic changes and their genetic basis, leading to the cytological diploidization of allopolyploids, are just beginning to be understood especially in wheat. However, the nature and mode of action of homoeologous recombination suppressor genes are poorly understood in other allopolyploids. The merger of two independent genomes causes a deep modification of their architecture, gene expression, and molecular interactions leading to the phenotype. We provide an overview of genomic changes and transcriptomic modifications that particularly occur at the early stages of allopolyploid formation.

Automated summary

Hybridization and polyploidy are important forces in plant adaptation and speciation. Interspecific gene flow generates adaptive genetic variants and increases yield in crops. The frequency of interspecific hybridization varies among taxa, with an estimated 9% occurrence. Allopolyploidy is more common than homoploid hybrid speciation. Chromosome doubling after hybridization is caused by cellular defects during meiosis. Unreduced gametes, formed at a frequency of 2.52% on average, result from altered spindle organization, disrupted kinetochore functioning, abnormal cytokinesis, or loss of meiotic division. Meiotic changes leading to cytological diploidization in allopolyploids are being understood, particularly in wheat. However, the understanding of homoeologous recombination suppressor genes in other allopolyploids is limited. The merger of two genomes leads to architectural, gene expression, and molecular interaction changes, resulting in phenotypic differences. This article provides an overview of genomic and transcriptomic changes during the early stages of allopolyploid formation.