The flow karyotype of Arabidopsis thaliana interphase chromosomes

The DNA contents of various aneuploid lines of Arabidopsis thaliana were measured by flow cytometry of 4', 6-diamidino-2-phenylindole-stained interphase nuclei in suspensions and compared with each other as well as with the wild-type. The fluorescence intensities for all lines were highly reproducible as were the deviations from the wild-type. The results allowed the estimation of the relative DNA contents of each Arabidopsis chromosome and of chromosome arms. The sum of the surplus values for all trisomics was close to the value expected for the haploid (2C) DNA content. Only the line with the smallest telotrisome (Tr 3A) did not significantly differ in DNA content from that of the wild-type. It is concluded that approximately 3% of the genome represents the limit for resolution of differences in DNA content in this system. Thus, the approach allows a fast and reliable screening for duplications and deficiencies extending to 3% of the Arabidopsis genome. Regarding chromosome sizes a comparison of the flow karyotype with existing karyotypes revealed differences which are discussed.