Aneuploidy refers to losses and/or gains of individual chromosomes from the normal chromosome set. The resulting gene dosage imbalance has a noticeable affect on the phenotype, as illustrated by
aneuploid syndromes, including
Down syndrome in humans, and by human solid
tumor cells, which are highly
aneuploid. Although the phenotypic manifestations of
aneuploidy are usually apparent, information about the underlying alterations in structure, expression, and interphase organization of unbalanced chromosome sets is still sparse. Plants generally tolerate
aneuploidy better than animals, and, through
colchicine treatment and breeding strategies, it is possible to obtain inbred sibling plants with different numbers of chromosomes. This possibility, combined with the genetic and genomics tools available for Arabidopsis thaliana, provides a powerful means to assess systematically the molecular and cytological consequences of aberrant numbers of specific chromosomes. Here, we report on the generation of Arabidopsis plants in which chromosome 5 is present in triplicate. We compare the global transcript profiles of normal diploids and chromosome 5 trisomics, and assess genome integrity using array comparative genome hybridization. We use live cell imaging to determine the interphase 3D arrangement of transgene-encoded fluorescent tags on chromosome 5 in trisomic and
triploid plants. The results indicate that
trisomy 5 disrupts gene expression throughout the genome and supports the production and/or retention of truncated copies of chromosome 5. Although
trisomy 5 does not grossly distort the interphase arrangement of fluorescent-tagged sites on chromosome 5, it may somewhat enhance associations between transgene alleles. Our analysis reveals the complex genomic changes that can occur in
aneuploids and underscores the importance of using multiple experimental approaches to investigate how chromosome numerical changes condition abnormal phenotypes and progressive
genome instability.