SUM Oylation Regulates Protein Stability Of FgCNB1 In Fusarium Graminearum

Fusarium head blight?FHB?caused by Fusarium graminearum has become the primary disease affecting the high and stable yield of wheat in China.FHB not only casues reduced yield of wheat,but it also affects the quality of wheat owing tomycotoxins during production and storage processes,which poses a serious safety hazard to mammals.The study on the pathogenic mechanism of F.graminearum is significant for the control of the disease.Calcineurin?CaN?is a protein phosphatase widely found in eukaryotes,and is composed of catalytic subunit CNA and regulatory subunit CNB.The activity of CaN is activated only after the C terminal of CNA binds to Ca²⁺or calmodulin.Ineukaryotes,calcineurin regulates signal transduction and responses to environmental stresses.In addition,calcineurin plays an important role in the pathogenesis inpathogenic fungi.In Cryptococcus neoformans calcineurin regulates pathogenicity via modulating the growth at 37?.In Magnaporthe oryzae,the inhibited function ofcalcineurin impaired the formation of appressorium,leading to the reduced virulence.In Ustilago maydis,calcineurin affects the efficient formation of filamentousdikaryons during mating and the formation of tumors upon inoculation of the plant.In our previous study,the SUMOylation pathway was found to regulate the DNA damage repair and pathogenicity in F.graminearum,and the mechanism ofSUMOylation in regulating DNA damage repair had been studied.This study tried to investigate the mechanism of SUMOylation in controlling the pathogenesis of F.graminearum.Two subuints of calcineurin,FgCNA1 and FgCNB1,were indentified to be the interacting proteins of SUMO by affinity capture assay.Further,the yeast two-hibrid and Co-IP?Co-Immunoprecipitation?assays confirmed that bothFgCNA1 and FgCNB1 were SUMOylated.Western Blot assays showed the SUMOylation regulated protein stability of FgCNB1 possibly via inhibitingubiquitin-mediated proteasome degradation.The possible SUMOylation sites of FgCNB1 were identified.The pathogenicity test showed that the SUMOylation pathway in F.graminearum may regulate pathogenicity through calcineurin.In this study,calcineurin was identified as a substrate of SUMOylation,and the SUMOylation of FgCNB1 is important for its protein stability,which may regulate the pathogenicity by the mechanism remaining to be further investigated in F.graminearum.