Phenotypic and Transcriptomic Changes Associated With Potato Autopolyploidization

Abstract

Polyploidy is remarkably common in the plant kingdom and polyploidization is a major driving force for plant genome evolution. Polyploids may contain genomes from different parental species (allopolyploidy) or include multiple sets of the same genome (autopolyploidy). Genetic and epigenetic changes associated with allopolyploidization have been a major research subject in recent years. However, we know little about the genetic impact imposed by autopolyploidization. We developed a synthetic autopolyploid series in potato (Solanum phureja) that includes one monoploid (1x) clone, two diploid (2x) clones, and one tetraploid (4x) clone. Cell size and organ thickness were positively correlated with the ploidy level. However, the 2x plants were generally the most vigorous and the 1x plants exhibited less vigor compared to the 2x and 4x individuals. We analyzed the transcriptomic variation associated with this autopolyploid series using a potato cDNA microarray containing $9000 genes. Statistically significant expression changes were observed among the ploidies for $10% of the genes in both leaflet and root tip tissues. However, most changes were associated with the monoploid and were within the twofold level. Thus, alteration of ploidy caused subtle expression changes of a substantial percentage of genes in the potato genome. We demonstrated that there are few genes, if any, whose expression is linearly correlated with the ploidy and can be dramatically changed because of ploidy alteration. Polyploids originate from either sexual reproduction via 2n gametes or somatic chromosome doubling. By traditional definition, there are two forms of polyploidy: allopolyploidy and autopolyploidy. These terms are often used to imply the mode of polyploid formation, but more accurately describe the degree of similarity between the subgenomes in polyploids. Allopolyploids have distinct subgenomes and typically originate from interspecific hybridization between divergent progenitor species. Autopolyploids have (nearly) identical subgenomes and typically originate from intraspecific hybridization (or self-fertilization through 2n gametes) or somatic chromosome doubling. Allo-and autopolyploids have traditionally been distinguished by modes of chromosome pairing and inheritance, with allopolyploids exhibiting bivalent pairing and disomic inheritance and autopolyploids exhibiting multivalent pairing and polysomic inheritance.A number of well-known polyploid plants of agricultural interest are classical allopolyploids, which include important crops such as bread wheat (2n ¼ 6x ¼ 42) and cotton (2n ¼ 4x ¼ 56). Studies of genetic and epigenetic changes associated with polyploidization have been focused mostly on newly synthesized allopolyploid materials 1 Present address:

Effect of polyploidization on morphology in two apple (Malus × domestica) genotypes

“…The results suggest that artificial genome doubling of diploid apple genotypes decreased plant vigour. Although polyploidization in plants is often associated with increased vigour, e.g., triploid apples (Sedysheva, Gorbacheva 2013) and hexaploid Hibiscus (Van Laere et al 2006, artificial genome doubling is very frequently associated with a decreased growth rate, e.g., in Citrus (Allario et al 2011;Guerra et al 2014), Spathiphyllum (Van Laere et al 2011, Platanus (Liu et al (Stupar et al 2007), and tetraploid Zea mays (Riddle et al 2006). Several observations show the increased vigour of triploid apple cultivars (Sedysheva, Gorbacheva 2013) and triploid Zea mays (Riddle et al 2006) over diploids but decreased vigour of higher ploidy levels and own observations of an increased vigour in tetraploid azalea; however, decreased vigour of hexaploids compared to diploids (Eeckhaut et al 2006) suggests that plant species potentially possess an optimal ploidy degree, below or above which its growth will be reduced.…”

Induction of tetraploid hardy rubber tree, <i>Eucommia ulmoides</i>, and phenotypic differences from diploid

“…In general, polyploid plants often possess larger cell sizes and sometimes larger biomass, height and girth (Comai 2005;Oselebe et al 2006), leaf size and thickness (Stupar et al 2007), fruit mass (Oselebe et al 2006;Vandenholt et al 1995), and stomata size (Miller et al 2012;Mishra 1997;Speckmann et al 1965). The phenotypic alterations sometimes affect secondary metabolites (Cohen et al 2013;Dhawan and Lavania 1996).…”

“…Laticifer and parenchyma diameters and epidermis size were almost the same size for tetraploids and diploids (Table 2, Figure 2). For many plant polyploids, scores for individual leaf areas or leaf thicknesses are higher than those of the normal diploid plants due to a larger increment of cell size (Miller et al 2012;Oselebe et al 2006;Stupar et al 2007), but the tendency toward increased cell size in E. ulmoides was less than that of other plant species.…”

Production of Autopolyploid Lowland Switchgrass Lines Through In Vitro Chromosome Doubling

“…The autooctoploid switchgrass lines could be used as a model to illustrate the consequences of polyploidy on the genome and gene expression levels in switchgrass [51]. In this case, the pairs of tetraploid and autooctoploid lines derived from the same SE callus lines, with similar or close genetic backgrounds, could be used to identify genes that are differently regulated by chromosome doubling through expression profiling [54][55][56]. It was also recently reported that switchgrass SE callus could be generated from in vitro culture of inflorescences [57].…”