The Functional Study Of Phytophthora Infestans Apoplastic Effector SCR50 In Induced Resistance

Phytophthora infestans can cause late blight of potato,causing enormous economic losses in agricultural production.Because of the rapid variation of Phytophthora infestans in the field,the control of Phytophthora infestans is a challenge.Chemical pesticides and cultivation techniques are the main methods to control Phytophthora.But the use of chemical pesticides will bring many negative effects,including pesticide residues in the environment and harm to human health.Therefore,it needs to be deeply analyzed at the molecular level to provide the basis for green prevention and control.The interaction mechanism between phytophthora and its host provides a new strategy for the biocontrol of late blight.A large number of effectors are secreted by Phytophthora infestans in the process of infecting plants,which regulate immunity response of plants.Therefore,functional analysis of effector is the key to the biocontrol of late blight.This study focuses on the molecular mechanism of the effector SCR50 causing Phytophthora infestans and biocontrol evaluation.The specific content is as follows:Phytophthora infestans effector SCR50 can induce plant immunity.SCR50 is a small cysteine-rich protein,consisting of 50 amino acids,including 27 amino acids of signal peptide and 23 amino acids of mature protein,among which 4 cysteine residues are conserved.We mapped its position in the whole genome.Found it on GSRs（Gene-Sparse Repeat Rich Regions）.This suggests that it evolved at a fast rate.Transcriptome data showed that the effector SCR50 was significantly up-regulated during infection.These results suggested that SCR50 might play an important role in the interaction.In addition,we have demonstrated its ability to induce cell death in a variety of Solanaceae plants.When the first cysteine of the N-terminal of SCR50 was mutated into alanine,its ability to induce cell death was enhanced.In order to investigate the plant signaling pathway of plant immunity induced by SCR50,we used VIGS technique to silence important genes in the immune signaling pathway.The results showed that BIK1,BAK1,MAPKKKα,Gα,Gβ1,and Gβ2 were involved in the process of SCR50-induced immune response in plants.The functional study of recombinant protein SCR50 in plant immunity and resistance.Previous results showed that the effector SCR50 had the ability to induce the immune response of plants.Next,we expressed and purified the SCR50 protein using the heterologous protein expression system,and tested whether the recombinant protein SCR50could improve the resistance of plants to Phytophthora.It was found in previous studies that the mutant SCR50^M1 had a stronger ability to induce cell death,so we chose the mutant SCR50^M1 for the resistance study We used prokaryotic expression system and yeast expression system to express and purify protein SCR50^M1.After the purified protein was obtained,it was detected in Nicotiana benthamiana whether the protein induced cell death,ROS burst and up-regulated expression of marker genes.The results showed that the recombinant proteins expressed in both prokaryotic and eukaryotic systems had no biological activity.Application of SCR50 in the control of crop dieases by Bacillus sp.In order to study the resistance of SCR50 and its application in agricultural production,we transfected SCR50into Bacillus to explore whether SCR50^M1 could improve plant resistance by inducing plant immune response,which is secreted by Bacillus.We used genetic transformation to transform effector containning the signal peptides into Bacillus OKB105 and BS102,respectively.Then the resistance to the disease was tested.The results showed that Bacillus carrying effector cannot enhance the resistance of tomato.In soybean and Phytophthora sojae system,both OKB105 and BS102 carrying SCR50^M1 could enhance etiolated seedlings resistance.The results showed that the effector protein SCR50^M1 secreted by Bacillus could improve plant resistance and provide material for later biological pesticides.