Verticillium Dahliae Toxin Induced Alterations Of Actin Cytoskeleton And Nucleolus In Arabidopsis Suspension Cells

In plant cells, actin cytoskeleton plays important roles in response to biotic and abiotic stresses. However, little has been known about the dynamics of actin cytoskeleton when cells are attacked by unphysical attacks from some stress factors such as elicitors. We report here that the toxin of Verticillium dahliae (VD-toxin) induced the changes of actin filaments in Arabidopsis suspension-cultured cells. When the cells were treated with low concentration VD-toxin, F-actin arrays were disrupted ordinally from cortex to nucleus-around, and then came the automatic recovery of them. The actin filaments in the perinuclear region showed more resistance to VD-toxin than the cortical ones. In contrast, when the cells were treated with high concentration VD-toxin, F-actin arrays were disrupted more severely and the disrupted actin cytoskeleton could not be recovered spontaneously. The treatment of high concentration VD-toxin on cells also induced the changes of nucleoli. At the early stages of the treatment, a nucleus had a single ring-shaped nucleolus. At the later stages, multiple smaller and brighter nucleoli emerged in a single nucleus. Disrupted actin cytoskeleton could be recovered by removal of the VD-toxin before the nucleoli were dyed. All these results showed that the actin cytoskeleton plays important roles in the early defense responses against VD-toxin in Arabidopsis suspension cells. The changes of the nucleoli induced by VD-toxin may be important characteristics that were accompanied by resistance-related cell death.