Function And Mechanism Of Cu-only Superoxide Dismutase PsSOD2 Duringn Puccinia Striiformis F.sp Tritici Infection Of Wheat

Accumulation of reaction oxygen species(ROS)following plant-pathogen interactions can trigger plant denfence responses and directly damage pathogens.For successful infection,pathogen have to evolve a corresponding tolerance mechanism.Thus,it is a precondition and foundation for pathogens to scavenge host-derived ROS to establish a parasitic relationship.However,the mechanisms protecting pathogens from host-derived oxidative stress remain unclear.A large number of studies have shown that superoxide dismutase(SOD)has played an important role in ROS scavenging.In this study,the functional identify of PsSOD2 in the wheat-Pst interaction was used to lay the foundation for further elucidating the mechanism of scavenging ROS.The main results are as follows:Searching from the wheat-Pst interaction cDNA libraries constructed in our lab,a 576 bp PsSOD2 gene was cloned,which encoded a polypeptide of 191 amino acids with a molecular weight of 19.8 kDa and pI of 9.23.Sequence analysis of PsSOD2 gene revealed that the gene contained secretory signal peptide and GPI signal peptide.Conserved domain analysis of PsSOD2 indicated that the gene codes a Cu-only SOD and PsSOD2 was highly conserved in Pst by sequence alignment.Phylogenetic analysis showed that the homologous gene of PsSOD2 was relatively conserved in basidiomycetes than ascomycetes.The quantitative real-time polymerase chain reaction(qRT-PCR)analyses the expression pattern of PsSOD2,which showed that PsSOD2 transcripts were up-regulated in the early infection stage.Prokaryotic expression and biochemical characterization revealed that PsSOD2 encoded a Cu-only SOD,the optimum pH was 10,and optimum temperature was 20?.The functional validation of signal peptide and analysis of subcellular localization suggest that PsSOD2 was anchored to the cell membrane of Pst under the action of secretory signal peptide and GPI signal peptide.Finally knockdown of PsSOD2 using a host-induced gene silencing(HIGS)system reduced the virulence of Pst,which was associated with ROS accumulation in HIGS plants.These results suggest that PsSOD2 is an important pathogenicity factor that is anchored to the cell membrane of Pst to contribute to Pst infection by scavenging host-derived ROS.