Aluminum (Al) represents a widespread environmental pollutant, with severe toxic impacts on plants.
In this study, we documented for the first time the structural and functional responses induced by two
concentrations of AlCl3 (10−2 M and 10−1 M) in the polytene chromosomes that characterize the chromatin
organization in the embryo suspensor cells of Phaseolus coccineus. Polytene chromosomes showed signs
of dose-dependent genotoxicity following AlCl3 treatments with a significant increase in both chromatin
stickiness and chromatin fragmentation. Polytene chromosomes specifically reacted to AlCl3 also in terms
of DNA and RNA puffing activity: with respect to the control, the treatments promoted ex-novo and/or
inhibited puff formation along chromosome arms, suggesting a fine modulation of the differential genome
activity in response to the treatments. The nuclei of suspensors from control and treated seeds showed
nucleoli mainly arranged by more than one NOR-bearing chromosome. In addition, AlCl3 treatments
affected the frequency of nucleoli organized by singular organizer chromosomes, with an increase in the
frequencies of nucleoli organized by chromosome II and a reduction in the frequencies of those organized
by chromosomes I or V. These results confirm that, also in our system, nucleolus may react as stress response
organelle.
Introductio
