Hydrogen Peroxide Induces Apoptosis Mediated By Metacaspase In Fusarium Graminearum

Fusarium graminearum is a fungal pathogen that infects many plant species,particularly cereals and corn.It is the causal agents of Fusarium head blight,leading to reduced yields and subsequent economic losses.Apoptosis is a form of programmed cell death with the importance for development and homeostasis of multicellular organisms.It is generally exist in animals,plants and bacteria.In fungi,apoptosis often happen at the different stages of life as heterokaryon incompatibility and hyphae autolyzed,in addition various factors including physical,chemical stress and antifungal compounds can induce apoptosis.Hydrogen peroxide?H₂O₂?is a kind of strong oxidant which can be used as an inducer of apoptosis,it is can directly through the cell membrane to play the role of oxidation.Experiments showed that H₂O₂ inhibits conidial germination and mycelial growth of F.graminearum.Treatment with H₂O₂ resulted in many apoptotic hallmarks,including nuclei deformation stained with DAPI,plasma membrane translocation of phosphatidylserine stained with annexin V-FITC and propidium iodine,loss of the mitochondrial membrane potential proved by JC-1,and DNA fragmentation observed with TUNEL assay.These results indicate that hydrogen peroxide induces apoptosis in F.graminearum.Furthermore,FITC-VAD-FMK used to detect metacaspase activation,results showed that activation were significantly increased after H₂O₂ treatment.Importantly,pretreatment with caspase inhibitor resulted in a dramatically reduced apoptotic rate,indicating that H₂O₂-induced apoptosis was dependent metacaspase.Furthmore,we found that both FgMCA1 and FgMCA2 were localized to the cytoplasm.These results indicate that hydrogen peroxide induces apoptosis undergoing serious typical characteristics of apoptosis depend on metacaspase in F.graminearum.