Functional analysis of the regulatory gene calR1 in calcimycin biosynthetic gene cluster

Abstract:

[Background] Calcimycin is an essential ionophoric antibiotic. The gene cluster for calcimycin biosynthesis has been cloned from the genome of Streptomyces chartreusis NRRL3882, but functions of some biosynthetic genes and regulatory genes in calcimycin biosynthesis remain unclear. [Objective] To study the functions of the putative regulatory gene calR1 encoding TylR-family transcriptional regulator in the biosynthetic gene cluster of calcimycin. [Methods] ThecalR1-knockout mutant and complementary strain were constructed by PCR-targeting and fermented, and their metabolites were analyzed by HPLC. The transcriptions of biosynthetic genes in ΔcalR1 mutant and wild-type strain were analyzed by RT-qPCR. [Results] ΔcalR1 mutant lost the ability to produce calcimycin, while the accumulation of cezomycin was observed. The complementary strain restored the production of calcimyc into a certain degree. The transcriptions of some essential genes, including calC, calG, and calU3, were substantially changed in ΔcalR1 mutant compared with those in the wild-type strain. [Conclusion] The putative TylR-family transcription regulatory gene calR1 is involved in calcimycin biosynthesis.