Regulatory Effect of Transcriptional Regulator TetR on the Synthesis of Conjugated Linoleic Acid in <i>Lactiplantibacillus plantarum</i> AR195

Conjugated linoleic acid (CLA) possesses anticancer, anti-inflammatory, and antiobesity properties, making it a significant research focus. In this study, we identified TetR, a TetR/AcrR family transcriptional regulator encoded by <i>AR1031</i>, as the transcriptional regulator of CLA synthesis in <i>Lactiplantibacillus plantarum</i> AR195. TetR binds to the promoter regions of the CLA synthesis genes, including the <i>cla</i> operon and <i>cla-hy</i>, thereby enhancing CLA biosynthesis. Knockout of <i>tetR</i> led to the downregulation of <i>cla-hy</i> by 68%, <i>cla-dh</i> by 86%, and <i>cla-dc</i> by 33%, resulting in reduced CLA yield. Further bioinformatic analysis and segmented electrophoretic mobility shift assay (EMSA) experiments revealed that TetR recognizes a conserved sequence (5'-TGTAGATTG-n₄-CTTCA-3') and binds to multiple sites within the regulatory region of the <i>cla</i> operon and <i>cla-hy</i>, thus promoting CLA biosynthesis. Overexpression of <i>tetR</i> increased the CLA yield by 7%. These findings provide precise insights into the regulation of CLA biosynthesis and suggest strategies for enhancing CLA production.