Characterize The Function Of Plant Membrane-Localized Receptor Kinases LecRK3 And RLK2 In Plant Immunity

Soybean root rot caused by Phytophthora sojae is a major threat of soybean production in China and causes serious economic losses every year.Due to lack of effective fungicides on P.sojae,growing disease-resistant cultivars is a major way to control P.sojae.However,the rapid genetic variation of P.sojae leads to loss of genetic resistance of the soybean cultivar,it is very important to select durable disease resistance genes for Phytophthora disease control.Plant cell membrane receptor like kinase plays an important role in plant immunity and growth.This study focus on lectin receptor kinases(LecRKs)and leucine-rich repeat receptor like kinases(LRR-RLKs).Through the identification of the receptor like kinase which can enhance plant resistance to disease,we hope to clarify the resistance mechanism of soybean to P.sojae and provide theoretical guidance for the prevention and control of P.sojae in production.Characterize The Function Of Lectin Receptor Kinase LecRK3 In Resistance To Phytophthora sojae:LecRKs are believed to be involved in plant disease resistance because of their extracellular lectin motif that can bind sugar specifically.In this study,LecRK genes in soybean were identified and their functions in soybean resistance to P.sojae were analyzed.In total,62 soybean LecRKs were predicted in the soybean genome,and the phylogeny relationship of LecRKs in Arabidopsis thaliana,N.benthamiana and tomato was analyzed.23 LecRKs were conserved among different plant species,while 29 are specific in soybean.The RNA-seq data analyses revealed that only 56 LecRK genes are expressed in soybean roots during the infection of P.sojae.9 LecRK genes were selected for further analyses.The expression levels of these 9 genes were detected in leaves during infection of P.sojae.Transiently expression of these genes in soybean hair roots leads to the indificiation of GmLecRK3 that positively regulates soybean resistance.The soybean hair roots expressing GmLecRK3 showing less oospore numbers and biomass of P.sojae when compared with control.In addition,overexpression of GmLecRK3 increases the expression level of defense-related genes GmPR1 and GmPR3 in soyean hair roots during infection of P.sojae.Characterize The Function Of LRR-RLK RLK2 In Plant Immunity:LRR receptors located at cell membrane play important roles in plant immunity.In previous studies,a key pathogenic factor of P.sojae PsXEGl was shown can be recognized by immne receptor RXEG1 and elicited cell death in N.benthamiana.In this study,We found the cell death induced by PsXEG1 and its two homologous proteins(PsXEG1-like1 and PsXEG1-like2)is also depends on RXEG1.In addition,a new LRR-RLK RLK2 was identified that participates in PsXEG1-induced defense signa1.PsXEG1,PsXEG1-likel and PsXEG1-like2 were transiently expressed on RLK2-silenced N.benthamiana leaves,the induced cell death was significantly reduced when compared to control.Similaryly,reactive oxygen species and defense marker gene CYP71D20 expression level induced by PsXEGl were also decreased in RLK2-silenced N.benthamiana.Meanwhile,the RLK2-silenced N.benthamiana showed enhanced susceptibility to Phytophthora parasitica.The result show that the silencing of RLK2 significantly reduced the resistance of N.benthamiana to P.parasitica.The above results indicate that RLK2 mediates the immune response activated by PsXEGl and regulates the disease resistance of plants to phytophthora.