Establishment Of A System For The Study Of Oomycete Effectors In Arabidopsis And The Preliminary Study Of AtBAG7 Regulating Heat-induced Plant Resistance

Oomycetes belongs to Stramenopilia.It includes many important plant pathogens such as Phytophthora,Peronospora and Pythium.It causes devastating disasters to agricultural development and the ecological environment system in worldwide.In the process of interaction between plants and oomycetes,oomycetes secrete a large number of effectors into plant cells to promote their own infection.The study of oomycete effectors is of great significance for in-depth understanding and revealing the pathogenic mechanism of pathogens.In this study,we intend to use the interaction system of the model pathogen Pseudomonas syringae and its host model plant Arabidopsis thaliana to establish an experimental system for studying the oomycete effectors.The system can screen for oomycete effectors with multiple phenotypes.And the phenotypic screening experiments of some effectors that are of great significance in the interaction between oomycetes and plants are performed using the well-established system.In addition,with global warming,the increase in temperature also has a great impact on the interaction between plants and pathogens.This study explored the role of Arabidopsis AtBAG7 in the interaction of plantsheat stress-Phytophthora.The main results and conclusions obtained are as follows:Establishment of a new system to study oomycete effectors in Arabidopsis thaliana:In this study,the type ? secretion signal of AvrPto and AvrRpm1 were constructed on the pUCP19 vector to form a modified vector.The C-terminus of the positive control AvrRpt2 was then constructed on the modified vector.The final vector was transferred into D36E which is the mutant strain of Pseudomonas syringae pv.Tomato strain DC3000 with all of the effector deletions.It was found that inoculation with Arabidopsis thaliana could still produce a strong hypersensitive response dependent on the resistance gene RPS2.It proved that the type ? secretion signal of AvrPto and AvrRpm1 have the function of secreting other effectors in this system,and the system is successfully established.Phenotypic screening of oomycete effectors on Arabidopsis thaliana using the DC3000 system:Part of the oomycete's effectors were selected in this study.Such as:8 RxLR effectors of Phytophthora capsici which are up-regulated in early or late stage of infection;9 core effectors of Phytophthora sojae which have high comprehensive expression.8 effectors of Phytophthora which have DNA or RNA binding domain;8 effectors of Pythium that induce resistance on Nicotiana benthamiana,and 2 effectors with special functions which our lab has previously studied.In order to explore the potential role of these effectors when they are secreted into plant cells,we used the established system for phenotypic screening and found that PsAvh180,PsAvh448,PsAvh167,and PoCRN12 were transferred into D36E which is the mutant strain of DC3000 with all of the effector deletions,after inoculation with Arabidopsis thaliana can make the Arabidopsis leaves get yellow.AtBAG7 regulates heat-induced resistance to Phytophthora in plants:BAG(B-cell lymphoma2-associated athanogene)is a family of anti-apoptotic genes.As a member of the BAG family in Arabidopsis,AtBAG7 is a molecular chaperone for endoplasmic reticulum(ER)localization and plays a central regulatory role in heat-induced unfolded protein response(UPR)and endoplasmic reticulum stress response.However,its role in plant response to pathogen infection is still unclear.Therefore,in this study we inoculated Arabidopsis wild type Col-0,AtBAG7 overexpressing plants HA-BAG7,AtBAG7 inserting mutant plants bag7 with Phytophthora capsici.The results showed that AtBAG7 negatively regulated the resistance of plants to Phytophthora.In addition,AtBAG7 is also involved in the response of plants to heat stress,so we explored the effect of heat stress treatment on plant resistance to Phytophthora and AtBAG7's contribution to it.It has been found that heat shock treatment significantly enhances the resistance of plants to Phytophthora,AtBAG7 is necessary for heat-induced plant resistance to Phytophthora,and also shows the double role of AtBAG7 in the interaction between plants and Phytophthora.At room temperature,it negatively regulates plant resistance,and positively regulates plant resistance after heat treatment.At the same time,the study found that AtBAG7 does not participate in part of the ETI(Effector-triggered immunity)pathway response(such as the HR response caused by the plant's recognition of AvrRpm1 and AvrRpt2).In addition,we further confirmed that the minimum temperature range for heat shock to induce AtBAG7 to enter the nucleus is 30?37?;through the above research.it has been shown that AtBAG7 is involved in the resistance of heat-induced plants to Phytophthora,and revealed its double role in the process of interaction between plants and Phytophthora.