Flow cytometry as a tool to investigate nuclear senescence in symbiotic and pathogenic systems

Arbuscular mycorrhizae have been reported to moderate negative effects (growth inhibition, necrosis, death) caused by soil-borne pathogenic fungi. In this paper, we assessed root viability with two DNA fluorescent flow cytometry stains that can be usefully combined to evaluate chromatin changes. Nuclei were extracted from arbuscular mycorrhizal (Glomus mosseae) and non-mycorrhizal tomato roots, infected or uninfected with Phytophthora nicotianae vat parasitica and watered with a low phosphate nutrient solution. Nuclei extracted from non-mycorrhizal roots infected with the pathogenic fungus showed lower fluorescence values after staining, compared to arbuscular mycorrhizal roots, suggesting that the presence of the pathogen may result in DNA loss and condensation. Infection by either fungus (symbiotic and pathogen) reduced the ratio of 4c to 2c nuclei in the differentiated root.