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.P.P. research lab is supported by P20_00971 grant from the Consejería de Transformación Económica, Industria, Conocimiento y Universidades/Cofinanciación FEDER 80%—Programa Operativo FEDER de Andalucía 2014-2020 and the PID2019-103996RB-I00 grant from the MCIN/AEI/10.13039/501100011033. T.N. and M.P. acknowledge the support of the Ministry of Science and Innovation of Spain (PID2020-118038GB-I00) and of the European Union (Marie Curie ITN, MEICOM 765212). M.P. is part of the International Plant Nucleus Consortium (IPNC) and COST Action n° CA 16212 ‘In Depth’. F.B. is a PhD fellow funded by the European Union (Marie Curie ITN, MEICOM 765212)