The TyrR regulon of Enterobacter ludwigii UW5

The TyrR transcription factor controls the expression of genes for the uptake and biosynthesis of aromatic amino acids in Escherichia coli. In the plant-associated and clinically significant proteobacterium Enterobacter ludwigii UW5, the TyrR orthologue was previously shown to regulate genes that encode enzymes for synthesis of the plant hormone indole-3-acetic acid and gluconeogenesis, indicating a broader function for the transcription factor. This study aimed to delineate the TyrR regulon of E. ludwigii by comparing the transcriptomes of the wild-type and a tyrR deletion strain. Our data show that TyrR regulates the expression of over 150 genes positively or negatively. The findings suggest that the E. ludwigii TyrR regulon has diverged from that of E. coli to include genes for survival in the diverse environments that this bacterium inhabits, and illustrate the expansion and plasticity of transcription factor regulons. RNA expression profiles were analyzed from quadruplicate cultures of wild-type and tyrR deletion mutant of Enterobacter ludwigii UW5.