Trichothecene fusarial toxins perturb the cell cycle in meristem-atic cells of Secale cereale L., Triticum aestivum L. and Vicia faba L

Abstract

Several species of Fusarium spp. which infect agricultural crops produce secondary metabolites exerting phytotoxic, zootoxic, cytotoxic and antibiotic effects. An effect of two trichothecene toxins, diacetoxyscirpenol (DAS; type A) and deoxynivalenol (DON; type B) on meristematic cells of T. aestivum, S. cereale and V. faba primary roots was investigated using flow cytometry and light microscopy. The G₂/G₁ ratio, mitotic index (MI) as well as phase indices were estimated in untreated, treated for 24 hours with the 10 mg/l solutions of toxins, and exposed to a 24-hour post-toxin incubation period root tips. Trichothecene toxins in most of cases increased the G₂/G₁ ratio (augmented proportion of 4C nuclei) and decreased MI. Excessive condensation of prophase chromosomes (cereals) or meta- and anaphase chromosomes (V. faba) and consequent changes in the phase indices were observed. Accumulation of cells with a 4C DNA content suggests that they were arrested at the G₂ phase of the cell cycle and could not enter mitosis. The observations confirmed that the trichothecene toxins DAS and DON can also act as inhibitors of the karyokinetic spindle, thus interfering with the progression of mitosis. For DAS, a more typical effect was to arrest the cell cycle in mitosis, while DON arrested the cells in the G₂ phase and prevented commencement of mitosis.

Key words:

• deoxynivalenol
• diacetoxyscirpenol
• flow cytometry
• meristematic cells
• mitotic index