Regulation of aureofuscin production by the PAS-LuxR family regulator AurJ3M

Abstract

aurJ3M(GenBank:EU697915.1), a 579 bp gene, whose deduced product (192 amino acid) was found to have amino acid sequence homology with some bacterial regulatory proteins. Computer-assisted analysis showed that AurJ3M is PAS-LuxR family regulatory protein, it combines a PAS domain with a helix–turn–helix (HTH) motif of the LuxR type. Gene deletion of aurJ3M from the S.aureofuscus SYAU0709 through gene replacement with the apramycin resistance gene aac (3) IV and the DNA fragment of the replication initiation site sequence OriT resulted in complete loss of aureofuscin production, indicating that AurJ3M is a positive regulator during the aureofuscin biosynthesis.Gene expression analyses in S.aureofuscus SYAU0709 and S.aureofuscus ΔaurJ3M by reverse transcriptase PCR (RT-PCR) indicated there no transcripts for the genes B、C、G、F、S0、S1、D in S.aureofuscus ΔaurJ3M, maintains some transcription of these genes although the levels is low. Transcription was also significantly reduced for gene A, and no difference in the transcription pattern was observed for the genes R、E and H, a similar transcription pattern was also observed for AurJ3M, A and B showed a different transcription pattern, while transcription of gene A in S.aureofuscus ΔaurJ3M when compared to the parental strain, no transcripts could be detected for gene B in the mutant; This result indicates that the deletion of aurJ3M gene doesn't have a polar effect on the transcription of genes located downstream from aurJ3M. In the ΔaurJ3M knockout mutant, except for the transcription of E、H、M and R, the transcription of other genes in the cluster was down-regulated, HPLC shows there no secondary metabolites was produced,aurJ3M has a pathway-specific regulation effect on the biosynthesis of aureofuscin. Aureofuscin had broad application prospects in food preservation, and enriched the resource pool of anti-fungal antibiotics of tetraphenyl macrolide in China.