Calculation of binding length of base-specific DNA dyes by comparison of sequence and flow cytometric data. Application to Oryza sativa and Arabidopsis thaliana

From biochemical experiments it has been found that AT- and GC-specific dyes need a certain number of consecutive bases of the same type for binding one dye molecule. From known base sequences the amount of bases included in dye binding can be calculated and compared with experimental data from flow cytometry. Oryza sativa and Arabidopsis thaliana are the first higher plants which are nearly completely (>90%) sequenced. From the published sequences the theoretical fluorescence intensity of base-specific dyes in relation to a base-unspecific dye is calculated for different binding lengths. These values are compared with the actual fluorescence intensities of nuclei analyzed by flow cytometry. For all investigated dyes (DAPI, Hoechst 33258, Hoechst 33342 (all AT specific) and Mithramycin A (GC specific)) a binding length of 1 bp results from the comparison of theoretical and experimental data. This is, however, in disagreement with former results on dye binding. The main reason for the discrepancy seems to be the remaining gap in the sequencing of the Arabidopsis genome.