Constitutive Heterochromatin Characterization By Differential Fluorochrome Binding Pattern in Ten Taxa of Abelmoschus medik. (Malvaceae)

Constitutive heterochromatin organization in the genome of Abelmoschus has been investigated with molecular cytogenetic tools using fluorescent stains CMA and DAPI for the first time in the genus. The double staining with fluorochromes CMA and DAPI had shown the presence of numerous and characteristics heterochromatic binding sites in the interphase nuclei, revealing the distribution pattern of GC and AT rich DNA sequences in the genome respectively. The lowest number of CMA⁺ binding sites was seen in A. enbeepeegearensis (2n=72) and the highest was recorded in A. caillei (2n=200). While the DAPI⁺ binding sites was recorded the lowest in A. enbeepeegearensis and the highest in A. caillei. The CMA⁺/DAPI⁺ binding sites was recorded the lowest in A. enbeepeegearensis while the highest in A. tetraphyllus var. tetraphyllus (2n=132). Range of CMA⁺ binding sites was lowest in A. angulosus var. grandiflorus (2n=66) while highest in A. caillei. Lowest range for DAPI⁺ binding sites was recorded in A. tuberculatus and the highest in A. tetraphyllus var. tetraphyllus. CMA⁺/DAPI⁺ binding sites range was lowest in A. enbeepeegearensis while the highest in A. caillei. The DAPI⁺ binding sites were more than CMA⁺ binding sites in all the 10 taxa studied. These CMA⁺ and DAPI⁺ binding sites tends to increase with the increase in chromosome numbers. Hence, it can be proposed that the distribution pattern of repetitive sequences within the heterochromatin block comprises more of AT rich than GC rich regions in all the 10 taxa analyzed in Abelmoschus. More of AT sequences than GC sequences suggest the genome instability of Abelmoschus.