Genetic Consequences of Polyploidy in Plants

Abstract

Most eukaryotes have a history of whole-genome multiplication events followed by a progressive return to a more diploid state. The initial state of polyploidization, in which more than two copies of the genome are present, is considered here and the various types of genetic consequences that occur depending on the nature of the polyploid formed. The degree of association of chromosomes in meiosis is determined by the relative homology and will affect the segregation of the chromosome which determines the genetic properties. If all the chromosomes are quite similar and form associations of like type, this situation is referred to as autopolyploidy. If the different sets of multiple chromosomes are sufficiently dissimilar to each other, then the homologs will pair in meiosis with themselves and segregate independently of the different but related chromosome pair. This situation is referred to as allopolyploidy. Gene expression in ploidal series typically follows a per cell level correlated more or less with the number of sets of chromosomes present. Variation of individual chromosomes, or aneuploidy, produces a greater number of modulations of gene expression in parallel to classical studies noting that aneuploids have greater impact on the phenotype than changes in the copy number of the whole genome. The genetic properties of odd-number ploidies, such as triploids, are also described as well as higher ploidal levels such as hexaploidy and octoploidy.