Fusarium Graminearum Growth Inhibition Due to Glucose Starvation Caused by Osthol

Abstract: The effects of osthol, a plant coumarin, on morphology, sugar uptake and cell wall components of Fusarium graminearum were examined in vitro by electron microscopy, ¹⁴C-labelling and enzyme activity detection. The results revealed that osthol could inhibit the hypha growth of F. graminearum by decreasing hyphal absorption to reducing sugar. After treatment with 100 μg·mL^-1 osthol for 24 h, many hyphal fragments of F. graminearum appeared. Microscopy observation showed that the cell walls of hyphal fragments blurred and the organelles of the cells degraded with the increasing vacuoles. The N-acetyl-D-glucosamine contents and chitinase activity both increased when hypha were treated with 100 μg·mL^-1 osthol, whereas the activity of β-1,6-glucanase remained unchanged. When F. graminearum fed with ¹⁴C glucose was treated with 100 μg·mL^-1osthol, glucose contents decreased to the lowest level, while the contents in non-osthol treated controls remained unchanged. These results suggested that chitinase activity might be related to glucose starvation under osthol treatment, and that the appearance of hyphae fragments maybe the results of the promoted chitinase activity which itself triggered chitin degradation.