SGE1 And SIX8 Regulate Pathogenicity Of Fusarium Oxysporum On Banana

The soil-borne disease Fusarium wilt of banana is caused by the fungus Fusarium oxysporum f.sp.cubense(Foc).Effectors play important roles in regulating the pathogenicity of Fusarium oxysporum.Using bioinformatics,molecular biology and proteomics approaches,effector genes were explored and analyzed.A transcriptional factor SGE1 and an effector were studied for their function on pathogenicity regulations.1.Functions of SGE1 transcription Factor.Deletion mutant of SGE1 was generated by homologous recombination.Phenotypic analysis indicated that deletion of SGE1 has no influence on vegetative growth,but impaired the conidiation of Foc 4.The SGE1 deletion mutant almost lost pathogenicity on banana plantlets.Microscopic observation indicated that the processes of fungus penetration and colonization were severely impaired in the SGE1 deletion mutant.Using SDS-PAGE analysis of the intracellular proteome,9 down-regulated protein spots and 3 up-regulated protein spots were identified in the SGE1 deletion mutant.iTRAQ analysis of extracellular proteome showed that 119 proteins were changed in the SGE1 deletion mutant.These results imply that SGE1 regulates the extracellular protein secretion which may have impact on pathogenicity of the fungal pathogen Foc 4.2.Functions of SIX8 effectorComparative genomic analysis of Foc 1 and Foc 4,two Foc 4-specific effector,SIX2 and SIX8 were identified.Mutant strain of two protein coding genes was constructed by homologous recombination.Phenotypic analysis showed that the SIX8 deletion mutant lost pathogenicity on banana plantlets.Construction the SIX8-FLAG fusion-expressing and complementary strain,Western blotting analysis demonstrated that SIX8 is a extracellular secretory protein.Microscopic observation indicated that the processes of penetration and colonization were severely impaired in the SIX8 deletion mutant.Transgenic Arabidopsis,transient expression in protoplasm and Western blotting analysis showed that SIX8 is post-translationally modified.Reactive-oxygen metabolism was significantly enhanced and resistance to Botrytis cinerea increased in SIX8 transgenic Arabidopsis.These results suggest that SIX8 plays important roles in regulation of the interactions of fungal pathogen Foc 4 and plants.Taken together,our results revealed that SGE1 and SIX play important role in regulating the pathogenicity of Foc4,which may provide a clue for control of this serious disease of banana.