Acetyltransferase OsACE2 acts as a regulator to reduce the environmental risk of oxyfluorfen to rice production

Insights into the synergistic effects of exogenous glycine betaine on the multiphase metabolism of oxyfluorfen in Oryza sativa for reducing environmental risks

Glycine betaine (GB), a secondary metabolite that regulates plant responses to biotic and abiotic stresses, may help reduce pesticide phytotoxicity, but this fact remains unestablished. This study investigated the physiological response of rice (Oryza sativa) to six dosages of oxyfluorfen (OFF) (0-0.25 mg/L) and two concentrations of GB (0 and 175 mg/L). GB treatment counteracted the considerable decrease in rice seedling growth caused by OFF treatment at doses higher than 0.15 mg/L. The biochemical processes and catalytic events associated with OFF-triggered degradation in rice were investigated using RNA-Seq-LC-Q-TOF-HRMS/MS after six rice root and shoot libraries were created and subjected to either OFF or OFF-GB. Rice treated with both GB and an ecologically relevant dose of OFF showed a marked upregulation of 1039 root genes and 111 shoot genes compared with those treated with OFF alone. Multiple OFF-degradative enzymes implicated in molecular metabolism and xenobiotic tolerance to environmental stress were identified by gene enrichment analysis. In comparison to treated with 0.25 mg/L OFF alone, exogenous GB administration decreased OFF accumulation, with the OFF concentration in roots being 44.47 % and in shoots being 51.03 %. The production of essential enzymes involved in the OFF decay process was attributed to certain genes with variable expression, including cytochrome P450, methyltransferase, glycosyltransferases, and acetyltransferases. Using LC-Q-TOF-HRMS/MS, 3 metabolites and 16 conjugates were identified in metabolic pathways including hydrolysis, acetylation, glycosylation, and interaction with amino acids in order to enhance OFF-degradative metabolism. All things considered, by reducing phytotoxicity and OFF buildup, external GB treatment can increase rice's resistance to oxidative stress caused by OFF. This study offers valuable insights into the function of GB in enhancing OFF degradation, which may have ramifications for designing genotypes that maximize OFF accumulation in rice crops and promote OFF degradation in paddy crops.

Metabolism of oxyfluorfen by actinobacteria Micrococcus sp. F3Y

Oxyfluorfen, a potent diphenyl ether herbicide, has raised significant environmental concerns due to its persistence, toxicity to non‒target organisms, and potential carcinogenicity. Microbial degradation plays a crucial role in mitigating its impact, yet complete mineralization pathways remain poorly understood. In this study, we isolated Micrococcus sp. F3Y, an oxyfluorfen‒degrading actinobacterium, and evaluated its degradation efficiency in yeast powder‒supplemented mineral medium (YPM) medium and oxyfluorfen‒contaminated soil. Optimal conditions, pH, temperature, initial optical density (OD600nm) were determined. Metabolites were analyzed via UPLC/Q‒TOF MS, and a putative gene cluster was identified through draft genome sequencing. Strain F3Y completely degraded 100 mg/L oxyfluorfen within 12 h under optimal conditions (pH 7.0, 30°C, OD600=2.0), maintaining over 55% efficiency at 25‒42°C and above 62% across a pH range of 6.5‒8.0. When the initial oxyfluorfen concentration was ≤150 mg/L, the degradation rate exceeded 74%. Moreover, in oxyfluorfen‒contaminated soil (0.06 mg/kg), inoculation with strain F3Y restored soybean (Glycine max) growth, increasing shoot length from 4.22 cm (severely inhibited) to 28.8 cm, a nearly 7‒fold improvement. Additionally, F3Y achieved 98.2% degradation of oxyfluorfen (50 mg/kg) within 25 d in unsterilized soil. Eleven metabolites, including six new intermediates, were identified. Based on these, two novel degradation pathways were proposed: one initiated by nitro reduction and the other by diaryl ether cleavage. Both pathways culminated in aromatic ring opening and complete mineralization. In addition, a potential 24.3 kb gene cluster, pao, was suggested. Comprising thirteen genes, it was hypothesized to participate in the ring cleavage of intermediate products during oxyfluorfen degradation. This study provided the first comprehensive evidence of Micrococcus mediated oxyfluorfen mineralization, offering new insights into actinobacterial metabolic versatility. With its high degradation efficiency, environmental resilience, and detoxification ability, F3Y was an ideal candidate for bioremediation. These finding not only enhanced the understanding of herbicide degradation but also provided a sustainable solution to address oxyfluorfen contamination in agricultural and natural ecosystems.

Breeding herbicide-resistant rice using CRISPR-Cas gene editing and other technologies

The emergence of herbicide-resistant weeds in crop fields and the extensive use of herbicides have led to a decrease in rice (Oryza sativa) yields and an increase in production costs. To address these challenges, researchers have focused on the discovery of new germplasm resources with herbicide resistance. The most promising candidate genes have been functionally studied and applied in rice breeding. Here, we review recent progress in the breeding of herbicide-resistant rice. We provide examples of various techniques used to breed herbicide-resistant rice, such as physical and chemical mutagenesis, genetic transformation, and CRISPR-Cas-mediated gene editing. We highlight factors involved in the breeding of herbicide-resistant rice, including target genes, rice varieties, degrees of herbicide resistance, and research tools. Finally, we suggest methods for breeding herbicide-resistant rice that could potentially be used for weed management in direct-seeding farm systems.

Comprehensive analyses show the enhancement effect of exogenous melatonin on fluroxypyr-meptyl multiple phase metabolisms in Oryza sativa for reducing environmental risks

The role of melatonin (MT), an essential phytohormone controlling the physiological and biochemical reactions of plants to biotic and abiotic stress, in alleviating pesticide phytotoxicity remains unclear. This study explores the effects of MT (0 and 200 mg/L) and six doses of fluroxypyr-meptyl (FLUME) (0-0.14 mg/L) on the physiological response of rice (Oryza sativa). FLUME exposure inhibited the growth of rice seedlings, with MT treatment ameliorating this effect. To determine the biochemical processes and catalytic events involved in FLUME breakdown in rice, six rice root and shoot libraries exposed to either FLUME or FLUME-MT were generated and then subjected to RNA-Seq-LC-Q-TOF-HRMS/MS analyses. The results showed that 1510 root genes and 139 shoot genes exhibited higher upregulation in plants treated with an ecologically realistic FLUME concentration and MT than in those treated with FLUME alone. Gene enrichment analysis revealed numerous FLUME-degradative enzymes operating in xenobiotic tolerance to environmental stress and molecular metabolism. Regarding the FLUME degradation process, certain differentially expressed genes were responsible for producing important enzymes, such as cytochrome P450, glycosyltransferases, and acetyltransferases. Four metabolites and ten conjugates in the pathways involving hydrolysis, malonylation, reduction, glycosylation, or acetylation were characterized using LC-Q-TOF-HRMS/MS to support FLUME-degradative metabolism. Overall, external application of MT can increase rice tolerance to FLUME-induced oxidative stress by reducing phytotoxicity and FLUME accumulation. This study provides insights into MT's role in facilitating FLUME degradation, with potential implications for engineering genotypes supporting FLUME degradation in paddy crops.

Insight into the relationship between metabolic enzymes and oxadiazon degradation in Oryza sativa for reducing environmental risks

Oxadiazon (ODZ) is extensively utilized in agricultural fields for weed control owing to its strong effectiveness. However, excessive loading of ODZ in water bodies and agricultural soils can lead to various environmental concerns. Therefore, it is crucial to understand the ODZ metabolic process and associated mechanisms in crops to assess the likelihood of ODZ contamination in the environment. This study aimed to assess the effects of ODZ on the growth and toxicological responses of rice (Oryza sativa). The growth of rice tissues was notably compromised with the increase in ODZ concentrations. RNA sequencing in combination with liquid chromatography-quadrupole-time-of-flight-high-resolution mass spectrometry/mass spectrometry (LC-Q-TOF-HRMS/MS) analysis allowed for the identification of numerous transcriptional components associated with ODZ metabolism. Four libraries comprising rice roots and shoots exposed to ODZ were RNA-sequenced in triplicate. The application of environmentally realistic ODZ concentrations upregulated the expression of 844 genes in shoots and 1476 genes in roots. Gene enrichment analysis revealed the presence of multiple enzymes involved in ODZ metabolism and detoxification. These enzymes play a critical role in mitigating environmental stress and facilitating xenobiotic metabolism. Notably, among differentially expressed genes, several key enzymes were identified, including cytochrome P450s, protein kinases, aminotransferases, and ATP-binding cassette transporters involved in the metabolic process. Using LC-Q-TOF-HRMS/MS, 3 metabolites and 13 conjugates were identified in multiple metabolic pathways involving oxidation, hydrolysis, glycosylation, acetylation, and methylation. This study successfully established a potential link between the specific metabolic products of ODZ and increased activities of their corresponding enzymes. Moreover, this study considerably elucidates the detailed pathways and mechanisms involved in ODZ metabolism. The study findings provide valuable insights into the development of genotypes for reducing ODZ residues in paddy fields and minimizing their accumulation in rice crops.

Uptake, translocation, accumulation, and metabolism of fluroxypyr-meptyl and oxidative stress induction in rice seedling

Fluroxypyr-meptyl (FLUME) is heterocyclic herbicide with internal absorption and transmission characteristics. Owing to its low cost and rapid efficacy, it has been widely used to control broad-leaved weeds in wheat, corn, and rice fields. However, the uptake, translocation, accumulation, and metabolism of FLUME in rice seedlings and the extent of oxidative stress induced by it remain largely unknown, which consequently restricts the comprehensive risk assessment of FLUME residues in the environment during rice production. Hence, we systematically investigated the growth and physiological responses of rice to FLUME and analyzed its uptake, translocation, accumulation, and metabolism in rice seedlings. The results indicated that under 0-0.12 mg/L FLUME treatment, only a small proportion of FLUME was translocated upward and accumulated in rice shoots following absorption via roots, with all the translocation factor values being < 1. Moreover, the distribution and enrichment ability of FLUME in rice seedlings were greater in roots than in shoots. Furthermore, we revealed that FLUME accumulation in rice seedlings evidently inhibited their growth and activated the defense system against oxidative stress, with an increase in the activity of antioxidant and detoxifying enzymes. In addition, multiple metabolic reactions of FLUME were observed in rice seedlings, including dehalogenation, hydroxylation, glycosylation, acetylation, and malonylation. Our study provides systematic insights into the uptake, translocation, accumulation, and metabolism of FLUME in rice seedlings as well as the oxidative stress induced by FLUME accumulation, which can help improve FLUME applications and environmental risk assessments in crops.