Abstract: [Objective] This study aimed to explore the ability of Burkholderia pyrrocinia JK-SH007 to synthesize the indole-3-acetic acid (IAA) and to elucidate the existence of a tryptophan-dependent indole-3-acetamide(IAM)IAA synthesis pathway in Burkholderia pyrrocinia JK-SH007.[Method] The ability of B. pyrrocinia JK-SH007 to synthesize IAA was detected by Salkowski colorimetry and enzyme-linked immunosorbent assay (ELISA) under the effect of L-tryptophan. The iaaM and iaaH genes were isolated from B. pyrrocinia JK-SH007 by PCR using specific primers, and their protein and phylogenetic relationships were analyzed by bioinformatics method. The differential expression of iaaM and iaaH genes in B. pyrrocinia JK-SH007 under L-tryptophan treatment were analyzed by real-time fluorescence quantitative PCR.[Result] B. pyrrocinia JK-SH007 strain was able to synthesize 15.663 μg·mL^-1 of IAA, and with L-tryptophan as precursor, the yield of IAA synthesized by B. pyrrocinia JK-SH007 increased significantly, reaching 44.404 μg·mL^-1. Both iaaM and iaaH genes contained a complete open reading frame. The full length of iaaM gene was 1 782 bp, encoding 593 amino acids which belongs to the Amino_oxidase super family; the full length of iaaH gene was 1 368 bp, encoding 455 amino acids which belongs to the Amidase super family. The expressions of iaaM and iaaH genes in B. pyrrocinia JK-SH007 were significantly increased under the treatment of L-tryptophan.[Conclusion] B. pyrrocinia JK-SH007 has the ability to synthesize IAA, L-tryptophan has a significant effect on its synthesis of IAA, and the cloned iaaM and iaaH genes have certain evolutionary conservatism, this study showed that B. pyrrocinia JK-SH007 exists indole-3-acetamide pathway.

Key words: Burkholderia pyrrocinia, IAA, IAM pathway, iaaM, iaaH