Then they were treated with different concentrations of H2O2 or AmB for 3 h. Protoplast cells of R. arrhizus were prepared in 2 ml of 0.5 mol l−1 glucose (pH 5.8) containing Novozym 234 (5 mg ml−1; Sigma-Aldrich Co.), chitinase (3 mg ml−1; Sigma-Aldrich Co.) and chitosanase (1.5 mg ml−1; Sigma-Aldrich Co.) and incubated at 30 °C for 3 h. Apoptosis was detected by fluorescence microscopy using Annexin V-FITC (Annexin V-FITC Apoptosis Detection KIt; Merck, Darmstadt, Germany) and propidium iodide (PI) to assess

cellular integrity and phosphatidylserine (PS) externalisation as previously described.[9] Each assay was repeated for at least three times. For terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL), protoplasts were washed twice in PBS and then fixed in 3.6% paraformaldehyde. TUNEL assay was performed according to the click here manufacturer’s

instructions as previously described.[10] Cells (2.5 × 106 spores ml−1) were collected by centrifugation, washed once Bortezomib molecular weight in 1 ml of PBS, resuspended in 1 ml of PBS containing various concentrations of H2O2 or AmB and incubated at 30 °C on a rotary shaker (100 rpm) for 3 h. The cells were stained with dihydrorhodamine123 (DHR123; Merck) at 37 °C for 2 h and then with PI. After staining, cells were analysed using flow cytometry. As shown in Fig. 1, the minimum fungicidal doses in R. arrhizus were 6 mmol l−1 H2O2 and 2 μg ml−1 AmB, at which point growth ceased and the fungi lost the ability to recover. Growth was not obviously affected below the concentrations of 0.6 mmol l−1 H2O2 and 0.03 μg ml−1 AmB, whereas cell viability was affected above 0.6 mmol l−1 H2O2 and 0.0625 μg ml−1 AmB. At the higher concentrations of 3.0–4.8 mmol l−1 H2O2 and 0.5–1.0 μg ml−1 AmB, growth ceased for more than 6 h and then recovered. Incubation of R. arrhizus mycelia with H2O2 and AmB for 3 h resulted in DNA fragmentation, which was visible as a smear using the agarose gel electrophoresis (Fig. 2). Figure 2 shows that DNA fragmentation appeared obviously after treatment with H2O2 (3.6 and 6.0 mmol l−1) and AmB (1 μg ml−1). DNA smears but not ladders

were observed. Apoptosis is characterised by several morphological and biochemical changes, such as membrane externalisation of PS on the cell surface, DNA fragmentation, chromatin condensation, etc.[10] This study observed whether heptaminol these apoptotic-like responses existed in the R. arrhizus induced by 3.6 mmol l−1 H2O2 and 1 μg ml−1 AmB for 3 h. The hallmark of apoptosis is the externalisation of PS from the inner to the outer leaflet of the plasma membrane. Hence, the annexin V-FITC/PI assay was used to examine the PS externalisation in R. arrhizus protoplasts. As shown in Fig. 3, green fluorescence indicating the binding of annexin V was found in most of the protoplasts from the fungi treated with H2O2 or AmB (Fig. 3a); the red fluorescence of PI represented dead cells (Fig. 3b). Another apoptosis marker is DNA fragmentation detected by the TUNEL assay.