Abstract:［Objective］In order to determine the effect of bkdR deletion on Cry protein production．We analyzed the transcriptional regulation of bkd gene cluster and the phenotype of bkdR mutant．［Methods］Sequence of bkd gene cluster in Bacillus thuringiensis was analyzed by sequence alignment．RT-PCRwas used to reveal the transcriptional units of the bkd gene cluster．bkdR insertion mutant was constructed by homologous recombination．Transcriptional activity was analyzed by promoter fusions with lacZ gene．Comparison of the Cry1Ac protein production was determined by protein quantitation．［Results］The bkd gene cluster was composed of eight genes．The ptb-bkdB formed one transcriptional unit．The transcriptional activity of ptb sharply decreased in sigL and bkdR mutants．Deletion of bkdR decreased the motility of cells，but no effect on growth，sporulation efficiency and Cry protein production．The bkd gene cluster is controlled by Sigma 54 and activated by BkdR． Deletion of bkdR has no effect on Cry protein production，but decreased the motility of the cells．［Conclusion］The bkd gene cluster is controlled by Sigma 54 and activated by BkdR． Deletion of bkdＲ has no effect on Cry protein production，but decreased the motility of the cells．It suggested that deletion of bkdR do not affect the Cry protein production the same as sigL mutant．It means decreasing of Cry protein productioninsigL mutant was not caused by only one EBP mutation，but might be multiple roles．