Identification Of The Regulating Gene Of Snc1-Related Mutant And Primary Studies Of Its Function Of The Disease Defense In Arabidopsis Thaliana

Innate immunity is critical for sensing and defending against microbial infection inmulticellular organisms. Plants have evolved sophisticated defense mechanisms againstpathogen infections, during which disease resistance gene (R-genes) play central roles inrecognizing pathogens and initiating downstream defense cascades.In Arabidopsis, a dominant mutant, suppressor of npr1-1, constitutive 1 (snc1), wasidentified previously that constitutively expresses pathogenesis-related (PR)genes andresistance against both Pseudomonas syringae pv maculicola (P.s.m.) ES4326 andPeronospora parasitica (P.p.) NOCO2. It is proved that snc1 which is one of the R genes at theupstream of the resistance pathway, can constitutive activation of disease resistance.AGR14 is one of the AGR series mutants on the background of snc1 mutant by T-DNAinsertion activation-tagging. By mutants screening and plasmid rescue for gene location, twoknockout genes in AGR14 have been identified which can recovery the phenotype of snc1, andtheir functions are unknown. The research contents and results of this paper as following:It is confirmed that the AGR14 is double mutant of BG and SG gene on the background ofthe snc1 mutant by using the methods of PCR or RT-PCR on the level of DNA or RNArespectively.The mutation of the BG gene can turn the phenotype of snc1 back into Col-0 partially,.rather than the SG gene by using the complementation experiment. It proves that BG geneplays an important role in the phenotype of the mutant AGR14, whose inactivation cansuppress the SNC1 gene partially.The overexpression experiment to analysis the function of the BG protein further more,the results show that BG-overexpression in Col-0 can change the phenotype of the plantsThe expression of the BG gene encoded protein in vivo or in vitro respectively suggeststhat the putative protein is existed in Arabidopsis which is characterized as a soluble and highmolecular weight protein. It is predicted that the function of this protein acts as atranscriptional corepressor mediating protein-protein interaction by WD40 repeat domain at theC-terminal and dimerization of the LisH structure domain at the N-terminal according to theanalysis of bioimformatics.The BG-GFP fused gene expression vector recombinant has been constructed andtransformed into the plant for encoded protein subcellular localization. The results show thatBG is localized in the nucleus of plant cells and predicted function act as a putativetranscriptional co-repressor.The bacteria and fungal infection experiments and the change of the PR gene ontranscriptional level show that AGR14 was constitutively expresses PR genes and moreresistance against both p.s.m. ES4326 and p.p. NOCO2 than Col-0, but less than snc1. Furthermore, the resistance of the BG-overexpressing plant to P.p.NOCO2 is associated with increasedexpression of the salicylate-regulated PR1 gene. It suggests that the BG gene is related with thedisease resistance function in plants.