Isoproturon-induced salicylic acid confers Arabidopsis resistance to isoproturon phytotoxicity and degradation in plants.

This study identified the effect of salicylic acid on degradation of isoproturon in Arabidopsis. Three T-DNA insertion mutant lines pal1-1, pal1-2 and eps1-1 defective in salicylic acid synthesis were tested, which showed higher isoproturon accumulation and toxic symptom in the mutants. When treated with 5 mg/L salicylic acid, these lines displayed a lower level of isoproturon and showed attenuated toxic symptom. RNA-sequencing study identified 2651 (1421 up and 1230 down) differentially expressed genes (DEGs) in eps1-1 and 2211 (1556 up and 655 down) in pal1-2 mutant plants (> 2.0 fold change, p< 0.05). Some of the DEGs covered Phase IIII reaction components like glycosyltransferases (GTs) and ATP-binding cassette transporters (ABCs). Using ultra performance liquid chromatography-time of fight tandem-mass spectrometer/mass spectrometer (UPLC-TOF-MS/MS), thirteen Phase I and four Phase II metabolites were characterized. Of these, two metabolites 1-OH-isopropyl-benzene-O-glucoside and 4-isopropylphenol-S-2-methylbutanoyl-serine have been identified and reported for the first time.