Study On The Mechanism Of BraCAP In The Interaction Between Chinese Cabbage And Plasmodiophora Bacteria

In the previous study,a protein was found,which was significantly up-regulated in Chinese cabbage roots after infected by plasmodiophora bacteria.To study its function,the full-length cDNA sequence was amplified.The expression pattern of the gene was analyzed by qRT-PCR and verified by in situ hybridization.The content of salicylic acid(SA)was determined after roots were infected by plasmodiophora bacteria.Expression analysis of the gene after SA inducted by qRT-PCR in roots and incidence of Arabidopsis mutants.The mechanism of the target gene in the interaction between Chinese cabbage and plasmodiophora bacteria was comprehensively analyzed.The results were as follows:1.Several differentially expressed proteins induced by p.brassicae infection in Chinese cabbage roots were studied.The cDNA sequences of the target genes corresponding to these proteins were found in the database.The specific primers of these genes were designed.The transcriptional levels of the genes in control(CK)and diseased(T)roots were detected by qRT-PCR.The results showed that the expression trends of these proteins at transcriptional level and protein level were almost consistent.Among them,expression difference of G15 was the most significant.2.NCBI Blastn showed that G15 had higher homology with ArabidopsisCAP gene and Brassica napusCAP gene,so G15 was named as BraCAP.The full-length cDNA sequence of BraCAP was obtained by cloning.The protein sequence domain analysis found that the BraCAP was a transmembrane PR1-like protein with a molecular weight of 19.37 KDa and an isoelectric point of 7.37.3.The expression analysis of BraCAP in roots,stems and leaves of Chinese cabbage by qRT-PCR showed that BraCAP had significantly high expression in roots.Then qRT-PCR was used to further analyze the expression of BraCAP in different stages roots after inoculating with plasmodiophora bacteria,and uninoclated roots was used as control.It was found that BraCAP was significantly higher expressed in inoculated roots than in uninoculated roots,especially highest in inoculated roots at diseased stage.This result further indicated that BraCAP was related to p.bacteria infection in Chinese cabbage.4.In situ hybridization showed that the hybridization signals began to appear in the inoculatet roots,and the hybridization signal was increased along with the time of the inoculation,which further proved that it was related to plasmodiophora bacteria infection in Chinese cabbage.5.The resistance identification of the Arabidopsis thaliana CAP-mutant and wild plant showd that the infection rate of the mutant was faster than that wild plants.It indicated that the deletion of CAP gene accelerated the infection of plasmodiophora bacteria.To undersand the resistant mechanism of BraCAP to plasmodiophora bacteria,the analysis of promoter element in BraCAP showed that the promoter region contained SA binding sites,indicating that the protein should play some role at the SA defense signal transduction pathway.qRT-PCR analysis found that SA treatment induced an increased expression for BraCAP.At the same time,the content of SA was increased after inoculation,and the content of salicylic acid was increased with the increase of inoculation time.It was further indicated that BraCAP plays an important role in the interaction mechanism of Chinese cabbage-plasmodiophora bacteria by SA increace,and BraCAP was resistant to plasmodiophora bacteria due to the high level of SA induced expression.