Abscisic acid (ABA) is a drought-stress-responsive hormone that plays an important role in the stomatal activity of plant leaves. Currently, ABA glycosides have been identified in apples, but their glycosyltransferases for glycosylation modification of ABA are still unidentified. In this study, the mRNA expression of glycosyltransferase gene MdUGT73AR4 was significantly up-regulated in mature apple leaves which were treated in drought stress by Real-Time PCR. It was hypothesised that MdUGT73AR4 might play an important role in drought stress. In order to further characterise the glycosylation modification substrate of glycosyltransferase MdUGT73AR4, we demonstrated through in vitro and in vivo functional validation that MdUGT73AR4 can glycosylate ABA. Moreover, the overexpression lines of MdUGT73AR4 significantly enhance its drought stress resistance function. We also found that the adversity stress transcription factor AREB1B might be an upstream transcription factor of MdUGT73AR4 by bioinformatics, EMSA, and ChIP experiments. In conclusion, this study found that the adversity stress transcription factor AREB1B was significantly up-regulated at the onset of drought stress, which in turn positively regulated the downstream glycosyltransferase MdUGT73AR4, causing it to modify ABA by mass glycosylation and promoting the ABA synthesis pathway, resulting in the accumulation of ABA content, and displaying a stress-resistant phenotype.

Natural products are one of the resources for discovering novel pesticide leads. Here, by molecular hybridization between the natural enamino diketone skeleton and the reported herbicide lead compound I, a series of 3-(1-aminoethylidene)-6-methyl-2H-pyran-2,4(3H)-dione derivatives (APD) were rationally designed, synthesized and tested for herbicidal activity in a greenhouse. The bioassay results showed that most of the target compounds possessed good herbicidal activity under pre-emergence conditions, of which the analog APD-II-15 displayed good pre-emergent herbicidal activity against Abutilon theophrasti Medicus, Amaranthus retroflexus L., Echinochloa crus-galli, Eragrostis curvula (Schrad.) Nees, Avena fatua L., Cyperus difformis L., Chenopodium album L., Ixeris denticulata, Plantago asiatica L., Capsella bursa-pastoris (Linn.) Medic and Flaveria bidentis (L.) Kuntze with > 60% inhibition even at a dosage of 187.5 g ha⁻¹, and displayed good crop safety for wheat, soybean, millet and sorghum at a dosage of 375 g ha⁻¹. The preliminary study of the molecular mode of action by RNA sequencing suggested that a growth inhibition of weeds by APD-II-15 might result from the disruptions of carbon metabolism and formation of a cytoskeleton. The present work indicated that APD-II-15 might be used as a novel herbicidal lead compound for further optimization.

To discover new acetyl-CoA carboxylase (ACCase) inhibiting-based herbicides, twenty-nine novel quinazolin-4(3H)-one derivatives were designed and synthesized based on the aryloxyphenoxypropionate motif. The bioassay results showed that most of the target compounds showed better pre-emergent herbicidal activity against monocotyledonous weeds in a greenhouse. Especially, when applied at 375 g ha⁻¹ under pre-emergence conditions, compound QPP-7 displayed excellent herbicidal activity against monocotyledonous weeds (i.e., E. crusgalli, D. sanguinalis, P. alopecuroides, S. viridis, E. indica, A. fatua, E. dahuricu, S. alterniflora) with inhibition rate >90%, and displayed excellent crop safety to O. sativa, T. aestivum, G. spp, and A. hypogaea. The study of structure-activity relationship (SAR) revealed that the herbicidal activity of target compounds is strongly influenced by the spatial position of R group and the bulk of R₁ group on quinazolin-4(3H)-one, and the (R = 6-F, R₁ = Me) pattern is confirmed as the optimal orientation. Furthermore, the molecular docking study and the good inhibitory activity of QPP-7 against E. crusgalli ACCase enzyme (IC₅₀ = 54.65 nM) indicated that it may be a ACCase inhibitor. Taken together, the present work demonstrated that compound QPP-7 could serve as a potential lead structure for further developing novel ACCase inhibiting-based herbicide.