Improving the herbicide resistance of 4-hydroxyphenylpyruvate dioxygenase SpHPPD by directed evolution

Improving the Herbicide Resistance of Rice 4-Hydroxyphenylpyruvate Dioxygenase by DNA Shuffling Basis-Directed Evolution

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is an ideal target for herbicide resistance genetic engineering. In this study, a mutant MFRR-2 with mesotrione resistance was screened from an Oryza sativa HPPD and mutant-Zea mays HPPD DNA shuffling library. The enzyme properties showed that although the stability of the mutant decreased in vitro, the enzyme activity of MFRR-2 at the optimum temperature of 25 °C was still equivalent to that of OsHPPD. Under 50 μM mesotrione treatment, MFRR-2 enzyme activity remained at approximately 90%, while the enzyme activity of OsHPPD decreased by approximately 50%. Surprisingly, Fe2+ was found to have an inhibitory effect on the enzyme activity. Then, the transgenic rice of the MFRR-2 gene showed approximately 1.5 times mesotrione resistance compared to OsHPPD transgenic rice. In conclusion, this study has conducted a beneficial exploration on the use of DNA shuffling for HPPD-directed evolution, and the mutant has potential application value for herbicide resistance genetic engineering.

Design, Synthesis, and Bioactivity of Novel Ester-Substituted Cyclohexenone Derivatives as Safeners

Tembotrione, a 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor, has been widely used in many types of plants. Tembotrione has been reported for its likelihood of causing injury and plant death to certain corn hybrids. Safeners are co-applied with herbicides to protect certain crops without compromising weed control efficacy. Alternatively, herbicide safeners may effectively improve herbicide selectivity. To address tembotrione-induced Zea mays injury, a series of novel ester-substituted cyclohexenone derivatives were designed using the fragment splicing method. In total, 35 title compounds were synthesized via acylation reactions. All the compounds were characterized using infrared spectroscopy, ¹H and ¹³C nuclear magnetic resonance spectroscopy, and high-resolution mass spectrometry. The configuration of compound II-15 was confirmed using single-crystal X-ray diffraction. The bioactivity assay proved that tembotrione phytotoxicity to maize could be reduced by most title compounds. In particular, compound II-14 exhibited the highest activity against tembotrione. The molecular structure comparisons as well as absorption, distribution, metabolism, excretion, and toxicity predictions demonstrated that compound II-14 exhibited pharmacokinetic properties similar to those of the commercial safener isoxadifen-ethyl. The molecular docking model indicated that compound II-14 could prevent tembotrione from reaching or acting with Z. mays HPPD (PDB: 1SP8). Molecular dynamics simulations showed that compound II-14 maintained satisfactory stability with Z. mays HPPD. This research revealed that ester-substituted cyclohexenone derivatives can be developed as potential candidates for discovering novel herbicide safeners in the future.

Effects of HPPD inhibitor herbicides on soybean root exudates: A combination study of multispectral technique and 2D-COS analysis

4-Hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor herbicides are widely used in modern agriculture. Plant root exudates (REs) play an important role in the adsorption, degradation, migration and transformation of pesticides in soil. In the present study, the structural affinity and interaction mechanism between four HPPD inhibitors (HPPDi) and soybean REs were investigated via multispectral technologies and two-dimensional correlation analysis (2D-COS). UV-vis absorption and fluorescence spectra showed that mesotrione, tembotrione, sulcotrione and topramezone effectively quench the intrinsic fluorescence of soybean REs through static quenching. The binding constant K_a revealed that the binding ability of HPPDi to soybean REs takes the following order: mesotrione > tembotrione > sulcotrione > topramezone. According to the thermodynamic parameters, the main interaction force between tembotrione, sulcotrione, topramezone and soybean REs is electrostatic interaction, while the main interaction force is a hydrogen bond or van der Waals force between mesotrione and soybean REs. The conformational changes of REs were attributed to HPPDi by 3D spectral evaluation. FTIR spectroscopy and 2D-COS analysis suggested that soybean REs mainly formed stable complexes with HPPDi through functional groups such as carbonyl, carboxyl, methoxy and nitrate, and the first binding groups were carbonyl and carboxyl. These results provide helpful information for the adsorption and desorption process of environmental pollutants on the surface of plants and soil.

Phytochemical Profile and Herbicidal (Phytotoxic), Antioxidants Potential of Essential Oils from Calycolpus goetheanus (Myrtaceae) Specimens, and in Silico Study

The essential oil (EO) of Calycolpus goetheanus (Myrtaceae) specimens (A, B, and C) were obtained through hydrodistillation. The analysis of the chemical composition of the EOs was by gas chromatography coupled with mass spectrometry CG-MS, and gas chromatography coupled with a flame ionization detector CG-FID. The phytotoxic activity of those EOs was evaluated against two weed species from common pasture areas in the Amazon region: Mimosa pudica L. and Senna obtusifolia (L.) The antioxidant capacity of the EOs was determined by (DPPH•) and (ABTS•+). Using molecular docking, we evaluated the interaction mode of the major EO compounds with the molecular binding protein 4-hydroxyphenylpyruvate dioxygenase (HPPD). The EO of specimen A was characterized by β-eudesmol (22.83%), (E)-caryophyllene (14.61%), and γ-eudesmol (13.87%), while compounds 1,8-cineole (8.64%), (E)-caryophyllene (5.86%), δ-cadinene (5.78%), and palustrol (4.97%) characterize the chemical profile of specimen B’s EOs, and specimen C had α-cadinol (9.03%), δ-cadinene (8.01%), and (E)-caryophyllene (6.74%) as the majority. The phytotoxic potential of the EOs was observed in the receptor species M. pudica with percentages of inhibition of 30%, and 33.33% for specimens B and C, respectively. The EOs’ antioxidant in DPPH• was 0.79 ± 0.08 and 0.83 ± 0.02 mM for specimens A and B, respectively. In the TEAC, was 0.07 ± 0.02 mM for specimen A and 0.12 ± 0.06 mM for specimen B. In the results of the in silico study, we observed that the van der Waals and hydrophobic interactions of the alkyl and pi-alkyl types were the main interactions responsible for the formation of the receptor–ligand complex.