Indole 3 acetic acid

Indole-3-acetic acid (IAA) and citric acid were purchased from Sangon Biotech (Shanghai, China). Methanol, formic acid, acetonitrile (ACN), indole, and isatin were purchased from Aladdin (Shanghai, China). Methoxyamine hydrochloride (MEOX), anthranilate, sodium dodecyl sulfate (SDS), ammonium bicarbonate, and urea were purchased from Sigma-Aldrich (Shanghai, China). N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS) was purchased from Supelco (Shanghai, China). Trypsin was purchased from Promega Corporation (WI, United States). All other reagents used in this study were of liquid chromatography–mass spectrometry (LC-MS) or chromatographically grade and commercially available. The mineral salt medium (MSM) used in this study was prepared according to the previous description (Yu et al., 2018b ). IAA and IAA analogs were added into MSM before autoclaving, and these compounds were stable after autoclaving. E. coli cells were cultivated in LB broth at 37°C as previously described (Yu et al., 2018b ).