Dictamnine suppresses the development of pear ring rot induced by Botryosphaeria dothidea infection by disrupting the chitin biosynthesis.

Ring rot induced by Botryosphaeria dothidea is a major cause of growth and postharvest losses in various fruits. There is an urgent need to develop green fungicides due to pesticide resistance and environmental pressure. Here, we demonstrated the efficacy of dictamnine (DIC, 4-methoxyfuro [2,3-ß] quinoline, purity 98%), a compound isolated from the stems and leaves of Clausena lansium, in effectively suppressing pear ring rot by inhibiting the mycelial growth of B. dothidea. The median effective concentration of DIC was 15.48 µg/mL. Application of DIC to B. dothidea resulted in structural disruption of the cell wall and plasma membrane, leading to mycelial deformation, breakage, and cell death. Transcriptome analysis revealed significant inhibition of the synthetic pathways for fungal cell wall and membrane components by DIC. Particularly, the expression of chitin synthase, a key enzyme of chitin synthesis, was prominently down-regulated. Moreover, the chitin content in DIC-treated B. dothidea mycelia exhibited a substantial dose-dependent reduction. Based on these results, it is promising to develop DIC as an antifungal pesticide for controlling ring rot disease in pear fruits. Our study provides new insights into the underlying mechanism through which DIC inhibits the mycelial growth of B. dothidea.

Uptake, Translocation, and Distribution of Cyantraniliprole in a Wheat Planting System.

Cyantraniliprole uptake, translocation, and distribution in wheat plants grown in hydroponics and soil conditions were investigated. The hydroponics experiment indicated that cyantraniliprole was prone to be absorbed by wheat roots mainly through the apoplastic pathway and predominately distributed in the cell-soluble fraction (81.4-83.6%) and ultimately transferred upward to leaves (TFleave/stem = 4.84 > TFstem/root = 0.67). In wheat-soil systems, the uptake of cyantraniliprole was similar to that in hydroponics. The accumulation of cyantraniliprole in wheat tissues was mainly affected by the content of soil organic matter and clay, resulting in the increased adsorption of cyantraniliprole onto soils (R2 > 0.991, P < 0.01), and was positively related to the concentration of cyantraniliprole in soil pore water (R2 > 0.991, P < 0.001). Besides, the absorption of cyantraniliprole by wheat was predicted well by the partition-limited model. These results increased our understanding of the absorption and accumulation of cyantraniliprole in wheat and were also helpful for guiding the practical application and risk evaluation of cyantraniliprole.

Antifungal active ingredient from the twigs and leaves of Clausena lansium Lour. Skeels (Rutaceae).

Two novel amides, named clauphenamides A and B, and twelve other known compounds were isolated from the twigs and leaves of Clausena lansium Lour. Skeels (Rutaceae). Their structures were elucidated on the basis of extensive spectroscopic analysis and comparison with data reported in the literature. Clauphenamide A (1) featured in the unit of N-2-(4,8-dimethoxyfuro [2,3-b]quinolin-7-yl)vinyl, and clauphenamide B (2) was a unprecedented N-phenethyl cinnamide dimer. Other known compounds belong to pyrrolidone amides (3 and 4), furacoumarins (7-10), simple coumarins (11-14), lignan (5) and sesquiterpene (6). Compounds 5, 6, 10 and 12 were separated from the genus (Clausena) for the first time, while 13 was isolated in the species (C. lansium) for the first time. The antifungal activities of the isolated compounds were assayed. As a result, at the concentration of 100 µg/ml, compared with the control (chlorothalonil, inhibition rate of 83.67%), compounds 1 and 2 were found to exhibit moderate antifungal activity against B. dothidea with inhibition rates of 68.39% and 52.05%, respectively. Compounds 11-14 also exhibited moderate activity against B. dothidea and F. oxysporum, with inhibition rates greater than 40%. In addition, compared with the control (chlorothalonil, inhibition rate of 69.02%), compounds 11-14 showed strong antifungal activity to P. oryzae, with inhibition rates greater than 55%. Among them, compound 14 has the strongest antifungal activity against P. oryzae, and the inhibition rate (65.44%) is close to that of the control chlorothalonil. Additionally, the structure-activity relationships of the separated compounds are also discussed preliminarily in this paper.

Emergence of Triazole Resistance in Aspergillus fumigatus Exposed to Paclobutrazol.

As a global health problem, the source of triazole resistance in Aspergillus fumigatus has gained much attention. This study was conducted to explore whether the triazole plant regulator paclobutrazol could evolve triazole resistance in A. fumigatus. The results indicated that two triazole-resistant strains with hereditary stability were isolated from liquid medium and soil. The up-regulation of cyp51A, cyp51B, AtrF, cdr1B, AfuMDR1, AfuMDR2, and AfuMDR4 played an important role in these resistant strains. The triazole-resistance in A. fumigatus could depend on the selective pressure of paclobutrazol concentration and exposure time. These results indicate that the application of paclobutrazol may result in the emergency of triazole resistance in A. fumigatus and thus have a potential risk for the treatment of invasive aspergillosis.

Prevalence of Azole-Resistant Aspergillus fumigatus is Highly Associated with Azole Fungicide Residues in the Fields.

Triazole resistance in Aspergillus fumigatus is a growing public health concern. In addition to its emergence in the therapy of invasive aspergillosis by triazole medicines, it has been frequently detected in agricultural fields all over the world. Here, we explore the potential link between residues of azole fungicides with similar chemical structure to triazole medicines in soil and the emergence of resistant A. fumigatus (RAF) through 855 500 km2 monitoring survey in Eastern China covering 6 provinces. In total, 67.3%, 15.2%, 12.3%, 2.9%, 1.5%, 0.4%, and 0.3% of the soil samples contained these five fungicides (tebuconazole, difenoconazole, propiconazole, hexaconazole, and prochloraz) of 0-100, 100-200, 200-400, 400-600, 600-800, 800-1000, and >1000 ng/g, respectively. The fractions of samples containing RAF isolates were 2.4%, 5.2%, 6.4%, 7.7%, 7.4%, 14.3%, and 20.0% of the samples with total azole fungicide residues of 0-100, 100-200, 200-400, 400-600, 600-800, 800-1000, and >1000 ng/g, respectively. We find that the prevalence of RAFs is positively (P < 0.0001) correlated with residual levels of azole fungicides in soils. Our results suggest that the use of azole fungicides in agriculture should be minimized and the intervals between treatments expanded to reduce the selective pressure toward the development of resistance in A. fumigatus in agricultural fields.

Chemical factors affecting uptake and translocation of six pesticides in soil by maize (Zea mays L.).

Uptake of residual pesticides in a soil by a certain crop plant may be governed by their physicochemical properties. Uptake and translocation of pesticides (imidacloprid, acetamiprid, tricyclazole, azoxystrobin, tebuconazole and difenoconazole) with the octanol/water partition coefficient (log Kow) ranging from 0.57 to 4.36 were investigated in soil with maize as a model plant. The results show that all tested pesticides in soil were uptaken by maize with accumulation amount of 27.73, 17.75, 18.96, 12.56, 10.66 and 2.13 µg for imidacloprid, acetamiprid, tricyclazole, azoxystrobin, tebuconazole and difenoconazole at 14 d, respectively. The accumulation amount was negatively correlated with adsorption coefficients and positively correlated with pesticide concentration in in situ pore water (CIPW). Root bioconcentration factor varied widely from 0.61 for imidacloprid to 974.64 for difenoconazole was positively correlated with log Kow and molecular weight but negatively with water solubility. Conversely, translocation factor varied from 0 for difenoconazole to 1.64 for imidacloprid was negatively correlated with log Kow but positively with water solubility. It determined that uptake, accumulation and translocation of the pesticides in soil by maize are governed by their physicochemical properties, especially log Kow. CIPW is an appropriate candidate to evaluate the accumulation of pesticides in maize from soil.

Characterization, genome functional analysis, and detoxification of atrazine by Arthrobacter sp. C2.

Residual injury of atrazine to the succeeding crops has been frequently reported. It is necessary to find a solution for the detoxification of atrazine contaminated soil. A high-efficient bacterial strain Arthrobacter sp. C2 for atrazine degradation was isolated in this study. The genomic information of the isolate C2, and its degradation characteristics and potential application in detoxification of atrazine contaminated soil were investigated. The results indicated that the isolate C2 genome contained 4,305,216 bp nucleotides, three plasmids, and 4705 coding genes. The degradation rates of atrazine at levels of 1, 10, 100 mg/L by the isolate C2 were 0.34, 1.94, 18.64 mg/L/d, respectively. The optimum temperature and pH for the isolate C2 to degrade atrazine were 30 °C and 7.0-9.0. Based on the metabolites detected by UPLC-TOF-MS/MS and genome annotation of the isolate C2, a common metabolic pathway of atrazine was proposed as that atrazine is firstly dechlorinated into hydroxyatrazine, and subsequently to N-isopropylammelide via dealkylation, and ultimately deaminated to cyanuric acid. Introduction of the isolate C2 into soil can enhance degradation of atrazine and thus eliminate the toxic effect of this herbicide on wheat growth. Our results indicate that the strain C2 could be a potential bioresource for bioremediation of atrazine contaminated soil.

Root Uptake of Imidacloprid and Propiconazole Is Affected by Root Composition and Soil Characteristics.

Residual pesticides in soil may be taken up by crops and negatively affect food safety. The uptake mechanism of imidacloprid and propiconazole was studied using wheat roots. The factors affecting root uptake were also studied with different crops and in different soils. Imidacloprid and propiconazole were taken up by wheat roots mainly through the symplastic and apoplastic pathways, respectively. Root protein and lipid contents were the main factors affecting the uptake and accumulation of imidacloprid and propiconazole by different crop roots, respectively. The uptake of imidacloprid and propiconazole in soil by wheat plants was linearly correlated with their concentrations in soil pore water, which were governed by soil characteristics. These results are helpful for understanding and estimating crop uptake of residual pesticides in soils.

Competitive Adsorption and Mobility of Propiconazole and Difenoconazole on Five Different Soils.

Propiconazole (PPC) and difenoconazole (DFC) are often combined for field applications. The resulted co-exsistence of PPC and DFC may have an effect on the fate of their individuals in soil. In this study, adsorption, desorption and leaching of PPC and DFC alone and their combinations were investigated in five different soils. Adsorption of PPC and DFC was significantly different on each soil with the Freundlich adsorption coefficients of 2.86-28.69 and 14.86-98.93 negatively correlated with soil pH, respectively. In addition, adsorption of PPC and DFC was declined by 27.12-37.59% and 17.28-25.35% with the presence of coexisting DFC and PPC, respectively. Mobility of PPC and DFC in tested soils was enlarged in coexisting system. The results indicate that adsorption, desorption and mobility of PPC and DFC were mainly affected by soil pH, and these behaviors of individual PPC and DFC were obviously altered by their co-existence.

Five-Year Survey (2014 to 2018) of Azole Resistance in Environmental Aspergillus fumigatus Isolates from China.

A total of 191 soil samples from Hangzhou, China, were submitted to detect non-wild-type (non-WT) Aspergillus fumigatus and its associated mechanisms. There were 2 (4.7%), 13 (12.4%), and 31 (23.1%) isolates identified as non-WT in 2014, 2016, and 2018, respectively. The resistant mutations of TR34/L98H, TR46/Y121F/T289A, and TR34/L98H/S297T/F495I were found in 3, 5, and 5 non-WT isolates. The G448S mutation, previously only found in clinical settings, was detected in A. fumigatus from soil samples.

Triazole resistance in Aspergillus fumigatus in crop plant soil after tebuconazole applications.

Aspergillus fumigatus is the primary agent of invasive aspergillosis (IA) causing high morbidity and mortality in immunocompromised patients. Triazole resistance in A. fumigatus and its sources have gained wide attention. For several years, environmental fungicides use has been proposed as the major cause for triazole resistance in A. fumigatus. However, there are few studies on azole-resistant A. fumigatus (ARAF) selected by triazole fungicides in agricultural systems. We studied the possible emergence of ARAF in the field after exposure to triazole fungicide tebuconazole. Our results showed that exposure to tebuconazole in soil selects for resistance to triazoles in A. fumigatus. The probability of ARAF developing in soils depends upon the concentrations of tebuconazole after application. We suggest that tebuconazole applications should be minimized to reduce selective pressure for the generation of ARAFs.

Increased triazole-resistance and cyp51A mutations in Aspergillus fumigatus after selection with a combination of the triazole fungicides difenoconazole and propiconazole.

Triazole-resistance in Aspergillus fumigatus is widespread. We evaluated whether triazole-resistance in A. fumigatus and its related cyp51A mutations, induced by a combination of the triazole fungicides difenoconazole and propiconazole, differs from resistance induced by the individual fungicides. Both difenoconazole and propiconazole can induce triazole-resistance in A. fumigatus. Resistance is much easier induced by formulated fungicides or a combination of these two fungicides compared with standard fungicides or individual fungicides, respectively. Six different mutations (G138S, G138D, H147Y, I246M, M263I and D430N) were identified in the induced resistant strains. The H147Y, I246M and M263I mutations were associated with triazole-resistance. This implies that the application of a combination of difenoconazole and propiconazole may result in higher triazole-resistance in A. fumigatus and more mutations in the cyp51A gene.

Subcellular distribution governing accumulation and translocation of pesticides in wheat (Triticum aestivum L.).

Root uptake, translocation, and subcellular distribution of six pesticides (dinotefuran, thiamethoxam, imidacloprid, imazethapyr, propiconazole, and chlorpyrifos) with Kow ranging from -0.549 to 4.7 were investigated in wheat to study transportation and accumulation of pesticides. The root bioconcentration factor (RCF) of pesticides decreased with water solubility (R2 = 0.6121) and increased with hydrophobicity (when the pH-adjusted log Kow > 2, R2 = 0.925), respectively. The translocation of neutral pesticides from roots to shoots increased positively with water solubility (R2 > 0.6484) but decreased with hydrophobicity (R2 > 0.8039). The subcellular fraction concentration factor (SFCF) increased linearly with hydrophobicity of the tested pesticides (R2 > 0.958). The log RCF was positively correlated with log SFCF in root cell walls (R2 = 0.9894) and organelles (R2 = 0.9786). Transportation of the pesticides from roots to stems and stems to leaves was adversely affected by the log SFCF of cell walls and organelles of roots (R2 > 0.7997) and stems (R2 > 0.6666), respectively. Hydrophobicity-dependent SFCF is a factor governing accumulation of pesticides in roots after uptake and their subsequent upward translocation.

Upward translocation of acetochlor and atrazine in wheat plants depends on their distribution in roots.

Residual acetochlor and atrazine in soils, resulting from their extensive application to maize plants, may affect product safety of the ultimate wheat crop. To determine the potential uptake and accumulation of acetochlor and atrazine by wheat plants, the uptake mechanism, translocation, and subcellular distribution of these two herbicides were studied through hydroponic experiments (10 mg L-1). The results indicated that acetochlor can be taken up through the apoplastic pathway and can accumulate in wheat roots with little upward translocation. However, atrazine could be taken up by roots through the symplastic pathway and subsequently transported to the stems and leaves. Little upward translocation of acetochlor in wheat plants was due to its preferential distribution into root organelles with higher lipid contents. Conversely, the low bioconcentration of atrazine in root organelles and cell walls after uptake led to its easy upward translocation. Uptake of acetochlor and atrazine by wheat roots and the distribution of atrazine to the stems and leaves were predicted well by using the partition-limited model. The obtained results indicated that residual atrazine in soil may be taken up by wheat roots and acropetally translocated, thereby posing a threat to product safety of wheat.

Mutation in cyp51A and high expression of efflux pump gene of Aspergillus fumigatus induced by propiconazole in liquid medium and soil.

Triazole resistance in Aspergillus fumigatus is a major cause of clinical inefficacy in the treatment of invasive aspergillosis (IA). The hypothesis that triazole fungicides have driven the development of resistance in A. fumigatus has garnered substantial attention due to the similar structure and global detection of antifungal resistant A. fumigatus (ARAF) isolates in the soil. However, there is little evidence linking the application of triazole fungicides to the emergence of ARAF in the soil. This study was conducted to test if the resistance in A. fumigatus and its associated mutations in cyp51A could be induced by propiconazole in liquid medium and soil. The results indicate that propiconazole can induce resistance by alteration of G138S in cyp51A, and the overexpression of cyp51A, AfuMDR3 and AfuMDR4. G138S in cyp51A was first detected in the soil and associated with resistance. The emergence of the ARAFs in the soil may depends upon the level of propiconazole, and the number of ARAFs in soil treated with propiconazole at 2- and 5-fold dose was much greater than those in soil treated at the recommended dosage. The current data indicate that propiconazole can induce triazole resistance in A. fumigatus and should be applied for agricultural purposes at levels at or below the recommended dosage to avoid the emergence of ARAF in the soil.

Uptake, Translocation, and Subcellular Distribution of Azoxystrobin in Wheat Plant ( Triticum aestivum L.).

The uptake mechanism, translocation, and subcellular distribution of azoxystrobin (5 mg kg-1) in wheat plants was investigated under laboratory conditions. The wheat-water system reached equilibrium after 96 h. Azoxystrobin concentrations in roots were much higher than those in stems and leaves under different exposure times. Azoxystrobin uptake by roots was highly linear at different exposure concentrations, while the bioconcentration factors and translocation factors were independent of the exposed concentration at the equilibrium state. Dead roots adsorbed a larger amount of azoxystrobin than fresh roots, which was measured at different concentrations. Azoxystrobin preferentially accumulated in organelles, and the highest distribution proportion was detected in the soluble cell fractions. This study elucidated that the passive transport and apoplastic pathway dominated the uptake of azoxystrobin by wheat roots. Azoxystrobin primarily accumulated in roots and could be acropetally translocated, but its translocation capacity from roots to stems was limited. Additionally, the uptake and distribution of azoxystrobin by wheat plants could be predicted well by a partition-limited model.

Characterization and genome functional analysis of a novel metamitron-degrading strain Rhodococcus sp. MET via both triazinone and phenyl rings cleavage.

A novel bacterium capable of utilizing metamitron as the sole source of carbon and energy was isolated from contaminated soil and identified as Rhodococcus sp. MET based on its morphological characteristics, BIOLOG GP2 microplate profile, and 16S rDNA phylogeny. Genome sequencing and functional annotation of the isolate MET showed a 6,340,880 bp genome with a 62.47% GC content and 5,987 protein-coding genes. In total, 5,907 genes were annotated with the COG, GO, KEGG, Pfam, Swiss-Prot, TrEMBL, and nr databases. The degradation rate of metamitron by the isolate MET obviously increased with increasing substrate concentrations from 1 to 10 mg/l and subsequently decreased at 100 mg/l. The optimal pH and temperature for metamitron biodegradation were 7.0 and 20-30 °C, respectively. Based on genome annotation of the metamitron degradation genes and the metabolites detected by HPLC-MS/MS, the following metamitron biodegradation pathways were proposed: 1) Metamitron was transformed into 2-(3-hydrazinyl-2-ethyl)-hydrazono-2-phenylacetic acid by triazinone ring cleavage and further mineralization; 2) Metamitron was converted into 3-methyl-4-amino-6(2-hydroxy-muconic acid)-1,2,4-triazine-5(4H)-one by phenyl ring cleavage and further mineralization. The coexistence of diverse mineralization pathways indicates that our isolate may effectively bioremediate triazinone herbicide-contaminated soils.