Increasing the resolution of chromosome analysis using pyrido[1,2-a]benzimidazoles

We studied the influence of three derivatives of pyrido[1,2-a]benzimidazoles (PBIs), which have DNA-intercalating properties, on plant mitotic chromosome condensation, in order to increase the resolution of chromosome analysis. The efficiency of the influence of these agents was assessed using the median chromosome length on chromosome slides, as well as by the number and size of chromosome DAPI bands. We used the third chromosome of Linum grandiflorum Desf. in these experiments. The chromosome was identified on the slides using its DAPI band pattern and a molecular marker, viz., the 5S rDNA site, which is located in the proximal region of the long arm of the chromosome. The influence of the well-known 9-aminoacridine (9-AMA) DNA intercalator, which is widely used in karyotype studies of short-chromosome organisms, was used as a control in all of the experiments. It was found that the influence of each of the three PBIs in the study on the root meristem of L. grandiflorum resulted in an increase in the median length of the third chromosome, the linear centromeric DAPI band size, and the number of intercalary DAPI bands. All three PBIs acted more efficiently than 9-AMA. The median chromosome length was increased by 15–40% and the number of intercalary bands increased by 1.5–3 times after PBI treatment, as compared to 9-AMA treatment. At the same time, 7-CF3-PBI, in a similar manner to 9-AMA, did not change the relative size of the centromeric DAPI band, while 7-NH2-PBI and 9-NH2-7-CF3-PBI gradually increased this parameter. It is concluded that these substances can be used as intercalating agents in cytogenetic studies in order to increase the resolution of chromosome analysis.