Molecular Reaction Mechanism Of Paclobutrazol And Uniconazole With Gibberellin Synthetase In Plant

Triazole plant growth regulators paclobutrazol?PBZ?and uniconazole?UCZ?are widely used in agricultural production,these two pesticides are chiral pesticides and show obvious enantioselectivity in delaying plant growth.It is speculated that the reason for this is that paclobutrazol and uniconazole have enantioselectivity in the inhibition of plant Gibberellin synthesis related enzymes,The enantioselectivity inhibition of enzymes by chiuniconazole enantiomers on the gene expression of gibberellin synthesis related enzymes in plants were studied by using rice seedlings as test plants.On the basis of homologral pesticides can provide theoretical guidance for the selection and rational utilization of active enantiomers of chiral pesticides.In this study,baseline separation of paclobutrazol and uniconazole enantiomers was achieved.The effects of paclobutrazol and y modeling and molecular docking,the enantiomeric differences of inhibition of paclobutrazol and uniconazole on gibberellin synthesis related enzymes were studied.At the same time,the distribution of paclobutrazol and uniconazole in soil,plant stems and leaves and the effects of paclobutrazol and uniconazole on the metabolism of gibberellin GA₁,GA₃,GA₄,GA₈and GA₉ in plants were studied.It was found that paclobutrazol and uniconazole had significant enantioselectivity in the regulation of gene expression of gibberellin synthesis related enzymes.S-?-?-PBZ and R-?+?-PBZ regulated genes expression amount?95%confidence interval?were 3.25±0.93 and 2.0±0.9 fold decrease than the controls,respectively.The inhibitory ratio of S-?-?-PBZ on gene expression amount of gibberellin synthesis related enzymes in rice was 1.6 times higher than that of R-?+?-PBZ.S-?+?-UCZ and R-?-?-UCZ regulated genes expression amount?95%confidence interval?were 2.14±0.53 and 1.9±0.65 fold decrease than the controls,respectively.The inhibitory ratio of S-?+?-UCZ on gene expression amount of gibberellin synthesis related enzymes in rice was 1.13 times higher than that of R-?-?-UCZ.The crystal structure models of ent-kaurene oxidase?KO?,ent-kaurenoic acid oxidase?KAO?,GA20-oxidase?GA20ox?,GA2-oxidase?GA2ox?and GA3-oxidase?GA3ox?were constructed by homology modeling.The binding of S-enantiomers and R-enantiomers of paclobutrazol or uniconazole with enzyme were significantly different in binding sites and binding energies.The binding energies of S-?-?-PBZ with CPS,KO,KAO,GA20ox and GA2ox were-6.521,-13.231,-18.654,-14.864,and-14.501kcal/mol,respectively.The binding energies of R-?+?-PBZ with CPS,KO,KAO,GA20ox and GA2ox were-17.747,-13.664,-13.901,-9.0856 and-12.415 kcal/mol,respectively.The inhibition ratio of S-?-?-PBZ on gibberellin synthesis is higher than that of R-?+?-PBZ,which may be related to CPS,GA20ox,GA2ox and GA3ox enzymes included in gibberellin synthesis.The binding energies of S-?+?-UCZ with CPS,KO,KAO,GA20ox,GA2ox and GA3ox were-19.141,-18.862,-12.476,-33.049,-32.476and-13.306 kcal/mol,respectively.The binding energies of R-?+?-UCZ to CPS,KO,KAO and GA20ox were-40.046,-18.701,-18.064 and-13.171 kcal/mol,respectively.The inhibition ratio of S-?+?-PBZ on gibberellin synthesis is higher than that of R-?-?-UCZ,which may be related to KO,GA20ox,GA2ox and GA3ox enzymes in gibberellin synthesis.The binding of paclobutrazol and uniconazole with gibberellin synthesis related enzymes occurs on hydroxyl,penta-heterocycles and benzene rings.Hydrogen bond,?-?stacking and polar interaction are the key forces driving the binding of paclobutrazol and uniconazole to gibberellin synthesis related enzymes.It can be seen from the molecular docking binding energy that the binding stability of uniconazole to gibberellin related enzymes is higher than that of paclobutrazol,which may be due to the carbon-carbon double bond in uniconazole molecules.The concentration pattern of paclobutrazol and uniconazole in soil-plant system was in the order of soil>stem>leaf.The contents of GA₁,GA₃,GA₄ and GA₈ in plant leaves were negatively related with the concentration of paclobutrazol and uniconazole.