The Topological Distribution of the Chromocenter in Panstrongylus megistus (Burmeister) Malpighian Tubule Cells Examined by Confocal Microscopy

Panstrongylus megistus (Burmeister) and Triatoma infestans (Klug), blood-sucking hemipterans in the Reduviidae family, are vectors of Chagas disease. Both species exhibit holocentric chromosomes and conspicuous heterochromatin bodies (chromocenters), but they differ in chromosome number and chromocenter structure and composition patterns. In the Malpighian tubule cells of T. infestans, the chromocenters are positioned close to the nuclear periphery throughout the life of the insect, with no apparent association with overall gene silencing. Because chromocenter topology may vary in different species of the same genus and the spatial distribution pattern of the chromocenter of P. megistus has not yet been described, we used confocal microscopy to evaluate the spatial organization of this heterochromatic body in the Malpighian tubule cells of this species during nymphal development and in the adult phase compared to data reported for T. infestans. Despite the differences in chromocenter composition, structural pattern, and size between P. megistus and T. infestans, the chromocenter of P. megistus nymphs and adults, similar to those of T. infestans, was found to occupy a nonincidental position close to the nuclear periphery. The topological pattern observed at the chromocenter of P. megistus, which is consistent with the previous report of highly concentrated dimethylated histone H3 lysine 9 residues at the nuclear periphery was not found to be directly related to gene silencing or modulation.