Mutational sceens in Arabidopsis aimed at identifying genes that are required for functionality of the pepper Bs3 restistance gene

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The AvrBs3 protein of the bacterial phytopathogen Xanthomonas campestris pv. vesicatoria (Xcv)is injected via the type III secretion system into the cytoplasm of its host plant pepper. AvrBs3translocates to the host’s nucleus, binds to and transcriptionally activates the promoter of thepepper Bs3 resistance (R) gene, resulting in a hypersensitive response (HR). Bs3 encodes astructurally atypical flavin monooxygenase that does not share homology with any known plantR protein. Preliminary work has shown that the transcription factor AvrBs3 and the “HR executer”Bs3 are functional not only in pepper but also in the model plant Arabidopsis, which is theprerequisite for genetic dissection of the Bs3-mediated immune reaction in Arabidopsis. To do soArabidopsis will be transformed with a reporter construct that contains Bs3 under transcriptionalcontrol of an estradiol inducible promoter. Mutant screens aim to uncover genes that the Bs3protein requires to execute a cell death reaction. After initial characterization of the observedArabidopsis mutants we will isolate the corresponding genes and characterize them at themolecular level. The long-term goal is to elucidate the function of the identified genes in the contextof the Bs3-mediated immune response.