Aneuploidy and Genetic Variation in the Arabidopsis thaliana Triploid Response

Abstract

Polyploidy, the inheritance of more than two genome copies per cell, has played a major role in the evolution of higher plants. Little is known about the transition from diploidy to polyploidy but in some species, triploids are thought to function as intermediates in this transition. In contrast, in other species triploidy is viewed as a block. We investigated the responses of Arabidopsis thaliana to triploidy. The role of genetic variability was tested by comparing triploids generated from crosses between Col-0, a diploid, and either a natural autotetraploid (Wa-1) or an induced tetraploid of Col-0. In this study, we demonstrate that triploids of A. thaliana are fertile, producing a swarm of different aneuploids. Propagation of the progeny of a triploid for a few generations resulted in diploid and tetraploid cohorts. This demonstrated that, in A. thaliana, triploids can readily form tetraploids and function as bridges between euploid types. Genetic analysis of recombinant inbred lines produced from a triploid identified a locus on chromosome I exhibiting allelic bias in the tetraploid lines but not in the diploid lines. Thus, genetic variation was subject to selection contingent on the final ploidy and possibly acting during the protracted aneuploid phase. (McClintock 1929). resolved, independent assortment produces mostly anThese studies introduced the idea that triploids could euploid gametes. As a result, the immediate progeny of produce viable aneuploids, which were mostly trisomics. triploids can be composed of a complex swarm of varied Variation for aneuploid production exists. For example, karyotypes, which differ in the number of copies of each triploids of cherry tomato produce more aneuploids than chromosome.

A haploid genetics toolbox for Arabidopsis thaliana

“…Here we crossed the synthetic diploid Wa-1 as a pollen parent to natural tetraploid Wa-1 female to generate triploid Wa-1 plants containing Wa-1 cytoplasm. This triploid was subsequently crossed as a female to synthetic diploid Wa-1 male (Col-0 cytoplasm) to produce triploid, aneuploid and diploid progeny 33 , all with Wa-1 cytoplasm ( Supplementary Fig. 5 shows the crossing strategy to maintain Wa-1 cytoplasm in the ploidy series).…”

“…However, a tetraploid TILLING plant carrying the desired mutant allele must be converted to diploid for easy genetic analysis. In fact, the cenh3-1 allele used to create the HI strain was originally isolated from a tetraploid TILLING population that conventionally required two transitional generations via a triploid bridge to generate a diploid CENH3/ cenh3-1 heterozygote 22,33,34 . With a HI strategy, we hypothesized that a tetraploid TILLING population can be converted to diploid by a single cross.…”

Aneuploidy: Cells Losing Their Balance

“…In some instances, chromosome gains or losses are even part of their evolution. There are, however, several wellstudied examples in maize, rice, and Arabidopsis where aneuploid plants grow significantly more poorly than their wild-type counterparts (McClintock 1929;Singh et al 1996;Henry et al 2005). Particularly, in maize and rice, the degree of poor growth correlates with the size of the additional chromosome ( Figure 1D).…”

The BOY NAMED SUE Quantitative Trait Locus Confers Increased Meiotic Stability to an Adapted Natural Allopolyploid of Arabidopsis

“…Tetraploid derivative of Arabidopsis thaliana ecotype Ler-0 (4x-Ler) was produced as previously described (Henry et al, 2005). The tetraploid Arabidopsis arenosa (Care-1) is a wild-collected accession corresponding to ABRC seed stock number CS3901.…”