Aureoverticillactam, a potent antifungal macrocyclic lactam from Streptomyces aureoverticillatus NH6, generates calcium dyshomeostasis induced cell apoptosis via the phospholipase C pathway in Fusarium oxysporum f. sp. cubense race 4.

Extensive efforts have been devoted to discover new bio-fungicides of high efficiency for control of Fusarium oxysporum f. sp. cubense race 4 (Foc4), a catastrophic soil-borne phytopathogen causing banana fusarium wilt worldwide. In this paper, aureoverticillactam (YY3) was verified to possess a potent antifungal activity against Foc4 for the first time, with the EC50 values of 20.80 μg/ml against hyphal growth, and 12.62 μg/ml against spore germination. To provide insight into its action mechanism, the cellular ultrastructures of Foc4 was observed with YY3 treatment and the results revealed that YY3 led to cell wall thinning, mitochondrial deformities, apoptotic degradation of the subcellular fractions and entocyte leakage. Consistent with these variations, the enhanced permeability of cell membrane and mitochondrial membrane also occurred after YY3 treatment. At the enzymatic level, the activity of mitochondrial complex III, as well as the ATP synthase, was significantly suppressed by YY3 at a concentration above 12.50 μg/ml. Moreover, YY3 elevated the cytosolic Ca2+ level to promote the mitochondrial ROS production. The cell apoptosis also occurred as expected. At the transcriptome level, key genes involved in phosphatidylinositol signaling pathway were significantly impacted, with the expression level of Plc1 elevated by approximately 4 folds. The expression levels of two apoptotic genes, casA1 and casA2, were also significantly elevated by YY3. Of note, the activation of phospholipase C was observed by YY3 treatment in Foc4. These findings indicate that YY3 exerts its antifungal activity via activating the phospholipase C-calcium-dependent ROS signaling pathway, which makes it a great potential bio-fungicide.