PURPOSE: To obtain a new gene promoter useful for making a plasmid vector capable of manifesting bacteria belonging to Pseudomonas genus.

CONSTITUTION: The subject gene promoter is manifestable in bacteria belonging to Pseudomonas genus, derived from Pseudomonas solanacearum and having a base arrangement of the formula. Pseudomonas solanacearum is transformed by a transposon inserted suicide vector and a bacterium stock expressing a vector gene by a host promoter is selected from the manifested bodies, chromosome DNA is extracted and purified, and fragments partly digested by a restriction enzyme are linked to phage vector EMBL3 and subjected to packaging. A phage containing lux gene promoter region is screened by plaque hybridization with lux gene as a probe, separated DNA fragments are introduced into a broad host retrieval vector, which is introduced from E. coli to Pseudomonas bacteria by conjugation to obtain DNA fragments containing the promoter region.