Coregulation of lux Genes and Riboflavin Genes in Bioluminescent Bacteria of Photobacterium phosphoreum

摘要

Investigation of the expression of the riboflavin (rib) genes, which are found immediately downstream of luxG in the lux operon in Photobacterium phosphoreum, provides more information relevant to the evolution of bioluminescence, as well as to the regulation of supply of flavin substrate for bacterial bioluminescence reactions. In order to answer the question of whether or not the transcriptions of lux and rib genes are integrated, a transcriptional termination assay was performed with P. phosphoreum DNA, containing the possible stem-loop structures, located in the intergenic region of luxF and luxE (Ω_A), of luxG and ribE (Ω_B), and downstream of ribA (Ω_c). The expression of the CAT (Chloram-phenicol Acetyl Transferase) reporter gene was remarkably decreased upon the insertion of the stem-loop structure (Ω_C) into the strong lux promoter and the reporter gene. However, the insertion of the structure (Ω_B) into the intergenic region of the lux and the rib genes caused no significant change in expression from the CAT gene. In addition, the single stranded DNA in the same region was protected by the P. phosphoreum mRNA from the S1 nuclease protection assay. These results suggest that lux genes and rib genes are part of the same operon in P. phosphoreum.