Effect of the fungal mycotoxin patulin on the chromatin structure of fission yeast Schizosaccharomyces pombe.

The fungal mycotoxin patulin is produced by several molds, especially by Aspergillus and Penicillium. The aim of this study was to clarify whether patulin causes alterations in plasma membrane permeability of Schizosaccharomyces pombe lead to cellular shrinkage charateristic to apoptosis or increases cell size indicating necrosis in cells. Transmission and scanning electronmicroscopy revealed that lower concentrations of patulin induced cellular shrinkage and blebbing, higher concentration caused expansion without cellular disruption. Large-scale morphological changes of individual cells were followed by time lapse video microscopy. Patulin caused the elongation and stickiness of cells or rounded up their shapes. To visualize chromatin structures of S. pombe nuclei upon patulin treatment, protoplasts were isolated from S. pombe and subjected to fluorescent microscopy. Chromatin changes in the presence of 50 μM patulin concentration were characterized by elongated nuclei containing sticky fibrillary chromatin and enlarged round shaped nuclei trapped at the fibrillary stage of chromatin condensation. Short (60 min) incubation of S. pombe cells in the presence of high (500 μM) patulin concentration generated patches of condensed chromatin bodies inside the nucleus and caused nuclear expansion, with the rest of chromatin remaining in fibrillary form. Longer (90 min, 500 μM) incubation resulted in fewer highly condensed chromatin patches and in nuclear fragmentation. Although, high patulin concentration increased the size of S. pombe size, it did not lead to necrotic explosion of cells, neither did the fragmented nuclei resemble apoptotic bodies that would have indicated programmed cell death. All these morphological changes and the high rate of cell survival point to rapid adaptation and mixed type of fungistatic effects.