Fig. 3 show that , in the presence of the -- AI-2 control reaction , low expression of the lsr -- lacZ-fusions occurs in the absence of luxS and , similar to what was shown in Fig. 2 , the fusions are induced to varying degrees Identification of LsrR : a protein responsible for mediating AI-2 regulation of transcription of the lsr operon The above results show that AI-2 induces the expression of the lsr operon .