Lentinan protects Caenorhabditis elegans against fluopyram-induced toxicity through DAF-16 and SKN-1 pathways.

Fluopyram, a SDH inhibitor fungicide, is widely used in agriculture to control fungi and nematodes. However, fluopyram has been proved toxic that caused damage to organs through oxidative stress. The development of natural extracts that can reduce oxidative damage is a promising method. Lentinan is isolated from Lentinus edodes and has been verified its antioxidant activity. In this study, Caenorhabditis elegans was used to evaluate the protective effects of lentinan against fluopyram-induced toxicity and the possible mechanisms. Results showed that lentinan pretreatment notably increased the survival rate of N2 nematodes by 15.0 % and extended the lifespan by 91.5 %, compared with the fluopyram treatment. Lentinan pretreatment reverted the inhibition of the locomotion and reproduction of C. elegans under the fluopyram stress. In addition, lentinan pretreatment significantly decreased the contents of ROS and MDA in N2 nematodes. Moreover, pretreated with lentinan significantly recovered the decreased activities of CAT, SOD, GST and SDH induced by fluopyram. Lentinan pretreatment enhanced the mRNA levels of daf-16 and skn-1 and their downstream genes in the nematodes compared with the fluopyram group. In daf-16 and skn-1 mutants, the lifespan, ROS and related genes expression were not significantly changed in lentinan pretreatment. Pretreated with lentinan significantly enhanced the fluorescence intensity of SOD-3::GFP and GST-4::GFP, and promoted the nuclear translocation of DAF-16 and SKN-1 under the fluopyram stress. In summary, these findings indicated that lentinan protected C. elegans from fluopyram-induced toxicity via DAF-16 and SKN-1.

Biocontrol Efficacy of Bacillus methylotrophicus TA-1 Against Meloidogyne incognita in Tomato.

Root-knot nematodes (RKNs) are harmful plant-parasitic nematodes of tomatoes which can cause significant yield losses. Therefore, there is increasing interest in exploring the application of bacterial nematicides. The bacterium Bacillus methylotrophicus TA-1 is a broad-spectrum biological control agent; however, its effect on RKNs control remains largely unclear. In this study, the toxicity of B. methylotrophicus TA-1 against Meloidogyne incognita was investigated in vitro, and the potential of B. methylotrophicus TA-1 to decrease infection of RKNs in tomato were evaluated in pot and field trials. Results showed that B. methylotrophicus TA-1 exhibited high nematicidal activity against second-stage juveniles (J2s) and eggs of M. incognita with 50% lethal concentration (LC50) values of 5.80 and 7.00 × 108 colony forming units (CFU)/ml, respectively. In the pot experiments and field trials conducted in 2020 and 2021, tomato plants treated with B. methylotrophicus TA-1 soil drench applied once at 3, 6, and 9 × 108 CFU/plant had significantly higher plant height and greater yield compared with the untreated control. Tomato yields of the treated plots with B. methylotrophicus TA-1 in 2 consecutive years' field trials were between 53.4 to 66.1 and 52.8 to 61.5 t/ha, while they were 49.7 and 48.2 t/ha in the untreated control for each year, respectively. The lowest population densities of M. incognita at 30 and 60 days after treatment were 119 and 135 J2s per 100 g soil in 2020 and 43 and 118 J2s in 2021 in TA-1-treated plots. The lowest gall index of 4.7 and 3.3 in 2020 and 2021, respectively, and the highest yield were all observed in the TA-1 at 9 × 108 CFU/plant treated plants, with no significant differences with the commercial control abamectin. These results provided a basis for further studies of B. methylotrophicus TA-1 formulations, application doses, frequencies, and mechanisms of action, which are necessary before it could be used as a component of integrated management programs to manage RKNs in tomato production.

Reduced Sensitivity to Tebuconazole in Botryosphaeria dothidea Isolates Collected from Major Apple Production Areas of China.

China has the largest acreage and is the greatest producer of apples in the world. Apple ring rot (ARR) caused by Botryosphaeria dothidea is one of the major diseases affecting apple fruit production. Tebuconazole, a sterol demethylation-inhibiting (DMI) fungicide, has been increasingly applied to manage ARR in China. Resistance to tebuconazole in field populations of B. dothidea may be selected and accumulate to higher degrees over time. Establishment of tebuconazole sensitivity monitoring programs is critically important for resistance management and effective ARR control. However, the resistance level of B. dothidea to tebuconazole in China remains largely unknown. In this study, in vitro mycelial growth assays of B. dothidea in media amended with tebuconazole were conducted, and the sensitivity of B. dothidea to tebuconazole was determined with a set of 390 isolates collected from the major apple production provinces in China between 2006 and 2014. Results showed that the 50% effective concentration (EC50) value ranged from 0.011 to 0.918, 0.040 to 1.621, and 0.052 to 1.925 µg ml-1 with a median value of 0.194, 0.386, and 0.782 µg ml-1 in the isolates collected in 2006, 2010, and 2014, respectively. The frequency distribution of EC50 for tebuconazole was a nonnormal distribution (P < 0.05), suggesting that subpopulations with reduced sensitivity to tebuconazole had emerged in these B. dothidea isolates. The frequency distribution of the B. dothidea isolates collected in 2006 fit a unimodal curve and could be regarded as the baseline sensitivity to tebuconazole. The resistance levels increased over time with the average occurrence frequency of 43.3% and resistance index of 0.38. Positive cross-resistance was observed between tebuconazole and metconazole, which is another DMI fungicide, but multiple resistance was not detected between tebuconazole and non-DMI fungicides. Our results demonstrated that regular long-term resistance monitoring combining with prudent fungicide use should be implemented to prolong the lifespan of tebuconazole in management of ARR in apples.

Management of Meloidogyne incognita on Cucumber with a New Nonfumigant Nematicide Fluopimomide.

Cucumber (Cucumis sativus L.) is an economically important vegetable crop in China. Southern root-knot nematode (Meloidogyne incognita) is a significant obstacle in cucumber production, causing severe root damage and yield losses. Moreover, resistance development to fosthiazate, and poor mobility of abamectin, have led to failure to control this nematode. It is of great interest to growers and the vegetable industry to explore novel nonfumigant nematicides that can provide adequate control in an environmentally friendly manner. Fluopimomide (FM), a new chemical having a similar structure to fluopyram, was shown to exhibit toxic effects on fungi and nematodes. The efficacy of FM to reduce infection of M. incognita in cucumber was evaluated under greenhouse and field conditions. In the greenhouse, FM at all test rates resulted in a 22.5 to 39.6% and 31.3 to 55.0% reduction in the population density of M. incognita in the soil at 30 and 60 days after treatment (DAT), respectively, compared with the nontreated control. FM at 500 and 750 g ha-1 reduced (P < 0.05) root galling, meanwhile increasing plant height compared with the nontreated control at 30 and 60 DAT. In the field trials, FM at 500 and 750 g ha-1 decreased the population density of M. incognita and root galling 57.2 to 69.9% compared with the untreated control, while enhancing cucumber yield in two consecutive years. Furthermore, FM at 500 g ha-1 combined with fosthiazate was the most effective treatment showing a synergistic effect on reducing population densities of M. incognita, which was significantly greater than either FM or fosthiazate by themselves. In summary, FM has considerable potential for managing M. incognita on cucumber.

Exposure to fluopimomide at sublethal doses causes oxidative stress in Caenorhabditis elegans regulated by insulin/insulin-like growth factor 1-like signaling pathway.

Fluopimomide is an innovative pesticide, widely used for agricultural pest management; however, little is known about its effect on non-target organisms. This study was designed to assess the potential risk of fluopimomide and the molecular mechanisms using Caenorhabditis elegans, a common model animal. The oxidative stress-related indicators were analyzed in C. elegans after exposure to fluopimomide for 24 h at three sublethal doses (0.2, 1.0, and 5.0 mg/L). The results demonstrated that sublethal exposure to fluopimomide adversely affected the nematodes growth, locomotive behaviors, reproduction, and lifespan, accompanying with enhanced of reactive oxygen species (ROS) generation, lipid and lipofuscin accumulation, and malondialdehyde content. In addition, exposure to fluopimomide significantly inhibited antioxidant systems including superoxide dismutase, catalase, glutathione S-transferase, and glutathione in the nematodes. Moreover, the expression of oxidative stress-related genes of sod-3, hsp-16.1, gst-4, ctl-2, daf-16, and daf-2 were significantly down-regulated, while the expression of skn-1 was significantly up-regulated. Further evidence revealed that daf-16 and skn-1 mutant strains of C. elegans significantly decreased ROS production upon fluopimomide exposure compared with the wild-type nematodes. Overall, our findings indicated that exposure to fluopimomide at sublethal doses caused oxidative damage, mainly associated with insulin/IGF-1-like signaling pathway in C. elegans. This is the first report of potential toxic effects of fluopimomide even at low concentrations, providing a new insight into the mechanisms of toxicity to C. elegans by fluopimomide.

Evaluation of a Small-Molecule Compound, N-Acetylcysteine, for the Management of Bacterial Spot of Tomato Caused by Copper-Resistant Xanthomonas perforans.

Bacterial spot caused by Xanthomonas spp. is one of the major diseases in tomato. Xanthomonas perforans is the main pathogen of bacterial spot on tomato in Florida. Currently, application of copper fungicides is the primary measure used to manage this disease. However, the development of copper resistance in X. perforans and accumulation of copper in the environment are major concerns for excessive use of copper-based products in agriculture. Due to its antibacterial properties and low environmental impact, N-acetylcysteine (NAC), a small molecule commonly used in medicine for human bacterial diseases, has been studied in agriculture for the control of plant bacterial pathogens, including X. citri and Xylella fastidiosa. This study evaluated the effect of NAC alone and in combination with copper on a copper-resistant X. perforans strain in vitro and its ability to control bacterial spot of tomato under greenhouse and field conditions. In vitro, the minimum inhibitory concentration of NAC against the X. perforans strain was 2,048 mg liter-1. NAC increased sensitivity of the copper-resistant X. perforans to copper in vitro when application of NAC was followed by copper application after 6 h. In greenhouse assays, NAC applied alone or in combination with copper significantly (P < 0.05) reduced the disease severity of bacterial spot on tomato compared with the untreated control. NAC at 100 mg liter-1 + copper at 300 mg liter-1 consistently exhibited synergistic effects against bacterial spot. In the field trials, NAC at 1,000 mg liter-1 + copper at 150 mg liter-1 significantly reduced disease severity compared with the untreated control. Results from this study demonstrated that NAC significantly reduced the disease severity of bacterial spot of tomato and enhanced the efficacy of copper against copper-resistant X. perforans, indicating that NAC could be applied for the effective management of bacterial spot of tomato.

NAP is involved in GA-mediated chlorophyll degradation and leaf senescence by interacting with DELLAs in Arabidopsis.

KEY MESSAGE: RGA/GAI and NAP interacted with each other, and NAP was involved in GA signaling as a role of regulating age-dependent and dark-induced leaf senescence in Arabidopsis. Leaf senescence is a significant biological process which is beneficial for plant growth, development, and generation alternation in Arabidopsis. Recent researches have shown gibberellins (GAs) could accelerate leaf senescence. Nevertheless, the GA signaling involved in leaf senescence process remains elusive. Here, we reported a new potential regulation mechanism of GA-mediated chlorophyll degradation and leaf senescence. In this study, we confirmed that NAP positively regulated age-dependent and dark-induced leaf senescence and NAP knockout mutant nap was hyposensitive to GA3 (an active form of GA) treatment. DELLA family proteins with highly conserved structural domain function as master growth repressors that integrated GA signaling and leaf senescence. We validated RGA and GAI could interact with NAP in vitro and in vivo, and subsequently impaired the transcriptional activities of NAP to induce SAG113 and AAO3 expression in nap protoplasts. Taken together, we suggest that NAP is a novel component of the regulatory network that modulates the progress of leaf senescence in GA signaling.

The bHLH transcription factor gene AtUPB1 regulates growth by mediating cell cycle progression in Arabidopsis.

Plant growth, development and interaction with the environment involve the action of transcription factor. bHLH proteins play an essential and often conserved role in the plant kingdom. However, bHLH proteins that participate in the cell division process are less well known. Here, we report that the bHLH transcription factor gene AtUPB1 is involved in mediating cell cycle progression and root development. In yeast cells, AtUPB1 inhibits cells proliferation and the cells had increased numbers of nuclei. UPB1 overexpression decreased the expression of the cell division marker CYCB1-1, and CDKA1 expression could overcome the defect of UPB1 overexpression. Moreover, UPB1 could directly bind to the promoter region of the SIM and SMR1 genes to regulate cell cycle. These results support a new role for AtUPB1 regulating root meristem development by mediating the expression of SIM/SMR1 genes.

Characterization of Antagonistic Bacillus methylotrophicus Isolated From Rhizosphere and Its Biocontrol Effects on Maize Stalk Rot.

Stalk rot is one of the most serious and widespread diseases in maize, and effective control measures are currently lacking. Therefore, this study aimed to develop a new biological agent to manage this disease. An antagonistic bacterial strain, TA-1, was isolated from rhizosphere soil and identified as Bacillus methylotrophicus based on morphological and biochemical characterization and 16S ribosomal RNA and gyrB gene sequence analyses. TA-1 exhibited a strong antifungal effect on the growth of Fusarium graminearum mycelium, with 86.3% inhibition at a concentration of 108 CFU per ml. Transmission electron microscopy showed that TA-1 could disrupt the cellular structure of the fungus, induce necrosis, and degrade the cell wall. Greenhouse and field trials were performed to evaluate the biocontrol efficacy of TA-1 on maize stalk rot, and the results of greenhouse experiment revealed that the bacterium significantly reduced disease incidence and disease index. Seeds treated with a 108 CFU ml-1 cell suspension had the highest disease suppression at 86.8%. Results of field trials show that seed bacterization with TA-1 could not only reduce maize stalk rot incidence but also increase maize height, stem diameter, and grain yield. The lipopeptide antibiotics were isolated from the culture supernatants of TA-1 and identified as surfactins and iturins. Consequently, B. methylotrophicus TA-1 is a potential biocontrol agent against maize stalk rot.

Effects of fumigation with 1,3-dichloropropene on soil enzyme activities and microbial communities in continuous-cropping soil.

The compound 1,3-D (1,3-dichloropropene) is a potential candidate soil fumigant due to the restrictions on methyl bromide (MB). To date, little is known about the soil microbial community changes induced by 1,3-D fumigation. Therefore, soil properties, related soil enzymes, genes encoding the key enzymes of ammonia oxidation in both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) and bacterial diversity were investigated to assess the effects of 1,3-D fumigation on the soil microbial community. The results exhibited that fumigation with 1,3-D caused accumulation of NH4+-N, but it led to decrease in the rate of NO3--N, and the concentration of NO3--N gradually recovered. At 12 weeks after transplant (WAT) of tomato seedlings, the concentration of NH4+-N and NO3--N were not statistically significant between the 1,3-D treatment groups and the untreated control group. A similar tendency was found for organic matter, soil pH, urease and protease activities. Moreover, quantitative real-time PCR (qPCR) showed that 1,3-D decreased total bacterial abundance, AOA-amoA and AOB-amoA genes. In addition, Illumina MiSeq sequencing analysis revealed that soil bacterial community diversities were significantly reduced at earlier sampling time points, and at later sampling time points, soil bacterial diversity gradually recovered, there was no significant difference compared to the control group. The present study provides useful information to evaluate the environmental safety of 1,3-D.

Synergistic Effect of Combined Application of a New Fungicide Fluopimomide with a Biocontrol Agent Bacillus methylotrophicus TA-1 for Management of Gray Mold in Tomato.

Gray mold caused by Botrytis cinerea can be a severe disease of tomato infecting leaves and fruits of tomato plants. Chemical control is currently the most effective and reliable method; however, application of fungicides has many drawbacks. The combination of biological control agents with newly developed fungicides may be a practicable method to control B. cinerea. Fluopimomide is a newly developed fungicide with a novel mode of action. Bacillus methylotrophicus TA-1, isolated from rhizosphere soil of tomato, is a bacterial strain with a broad spectrum of antimicrobial activities. Little information is currently available about the effect of fluopimomide and its integrated effect on B. cinerea. Therefore, laboratory, pot, and field experiments were carried out to determine the effects of fluopimomide alone and in combination with B. methylotrophicus TA-1 against gray mold on tomato. The in vitro growth of B. methylotrophicus TA-1 was unaffected by 100 mg liter-1 fluopimomide. Inhibition of B. cinerea mycelial growth was significantly increased under combined treatment of fluopimomide and B. methylotrophicus TA-1. In greenhouse experiments, efficacy against gray mold was significantly greater by an integration of fluopimomide and B. methylotrophicus TA-1 than by either alone; control efficacy of fluopimomide at 50 and 100 g ha-1 in combination with B. methylotrophicus TA-1 at 108 colony-forming units (cfu) ml-1 reached 70.16 and 69.32%, respectively, compared with the untreated control. In both field trials during 2017 and 2018, control efficacy was significantly higher for the combination of fluopimomide at 50 and 100 g ha-1 in combination with B. methylotrophicus TA-1 than for either treatment alone. The results from this study indicated that integration of the new fungicide fluopimomide with the biocontrol agent B. methylotrophicus TA-1 synergistically increased control efficacy of the fungicide against gray mold of tomato.

Potential of a Small Molecule Carvacrol in Management of Vegetable Diseases.

Carvacrol, a plant-derived volatile small molecule, is effective against various agents that can cause damage to humans, the food processing industry, and plants, and is considered a safe substance for human consumption. In this short communication, previous studies on the effectiveness of carvacrol against various agents, particularly plant pathogens and their associated mechanisms are described. In our study, carvacrol was found to be effective on media against several soilborne pathogens and in planta against three foliar pathogens (Xanthomonas perforans, Alternaria tomatophila, and Podosphaeraxanthii) of important vegetable crops in south Florida of the United States. Current research findings indicated that the effectiveness of carvacrol against various plant pathogens tested was associated with its direct bactericidal/fungicidal effect, which was affected greatly by its volatility. Development of new formulations to overcome the volatility and to prolong the effectiveness of carvacrol was also presented. Our studies on carvacrol suggested that, with advanced development of new formulations, carvacrol could be used as a promising tool in the integrated pest management for bacterial, fungal, and viral pathogens of important vegetable crops in Florida, the USA, and the world.

Effect of Abamectin on the Cereal Cyst Nematode (CCN, Heterodera avenae) and Wheat Yield.

The cereal cyst nematode (CCN, Heterodera avenae) is a major pest in wheat and until now there is no pesticide registered to control this pest in China. Development of effective methods of controlling CCN is urgently needed. Abamectin is a biological pesticide that has a high nematicide activity. However, the efficacy of abamectin soil application to control CCN in wheat and its effect on yield in China remains unknown. Therefore, laboratory, greenhouse, and field tests were carried out to evaluate the potential of abamectin soil applications for CCN control and improvement of wheat yield. Laboratory tests showed that abamectin exhibited knockdown toxicity to CCN, with LC50 and LC90 values 9.8 and 59.4 mg liter-1. Greenhouse experiment and field trials showed that soil applications of abamectin provided significant CCN control and higher straw dry weights and wheat grain yields. There was an 8.5 to 19.3% yield increase from the various abamectin treatments compared with the control. The results of this study demonstrated that abamectin exhibited a high nematicidal activity to H. avenae and adequate performance to enhance wheat crop yields.

Comparison of Two Acute Toxicity Test Methods for the Silkworm (Lepidoptera: Bombycidae).

Silkworm (Bombyx mori) is an economically important insect and an ideal nontarget organism to study the environmental assessment of pesticides. Two acute toxicity test methods, leaf-dipping and quantitative spraying, with five insecticides, were compared for pesticide risk assessment. Based on LC50 values of these insecticides by both methods, the order of toxicity levels of five insecticides tested against silkworm was as follows: emamectin benzoate>lambda-cyhalothrin>imidacloprid>chlorpyrifos>dimethoate. Means of relative confidence interval values for individual insecticides of leaf-dipping and quantitative spraying method were-emamectin benzoate (22.55 and 19.03%), lambda-cyhalothrin (18.03 and 17.71%), imidacloprid (19.21 and 16.96%), chlorpyrifos (17.20 and 15.97%), and dimethoate (17.78 and 15.81%). The coefficient of variation values were-emamectin benzoate (17.74 and 5.44%), lambda-cyhalothrin (21.15 and 5.16%), imidacloprid (13.01 and 5.65%), chlorpyrifos (16.72 and 4.85%), and dimethoate (28.36 and 7.93%). The results of the study show that the quantitative spraying method is more effective than the leaf-dipping method in precision and reproducibility. The results of this study will offer a useful reference for selecting a more scientific and rational method for pesticide risk assessment.

Resistance Selection and Characterization of Chlorantraniliprole Resistance in Plutella xylostella (Lepidoptera: Plutellidae).

The diamondback moth, Plutella xylostella (L.), is considered one of the most damaging lepidopteran pests, and it has developed resistance to all conventional insecticide classes in the field. Chlorantraniliprole is the first commercial insecticide that belongs to the new chemical class of diamide insecticides. But, P. xylostella have already shown resistance to chlorantraniliprole in China. After 52 generations of selection with chlorantraniliprole, ∼48.17-fold resistance was observed. The resistant strain showed cross-resistance to flubendiamide (7.29-fold), abamectin (6.11-fold), and cyantraniliprole (3.31-fold). Quantitative real-time polymerase chain reaction analysis showed that the expression of the ryanodine receptor gene was higher in the resistant strain than that in the susceptible strain. Enzyme assays indicated that cytochrome P450 activity in the resistant strain was 4.26 times higher compared with the susceptible strain, whereas no difference was seen for glutathione-S-transferase and esterase. Moreover, the toxicity of chlorantraniliprole in the resistant strain could be synergized by piperonyl butoxide, but not by diethyl maleate, and S,S,S-tributyl phosphorothioate. These results can serve as an important base for guiding the use of insecticide in field and delaying the development of pests that are resistant to the insecticides.

Increasing Cyetpyrafen Spray Volume and Ozone Spray Improves the Control Effects against Two-Spotted Spider Mite (Tetranychus urticae) in Strawberries.

The two-spotted spider mite (Tetranychus urticae) is a constant threat to greenhouse strawberry production. The application of synthetic acaricides is the main method of controlling T. urticae. However, resistance development to traditional acaricides reduces their efficacy and eventually leads to control failure. It is important for strawberry growers to look for new acaricides and application technologies that can limit the harmfulness of T. urticae in environmentally friendly ways. In the current study, laboratory toxicity tests and field trials were performed to screen high-efficiency acaricides, and then application technologies were improved to enhance the management of T. urticae. In the laboratory toxicity tests, the results showed that the LC50 (median lethal concentration) value of cyetpyrafen, cyenopyrafen, cyflumetofen, bifenazate, abamectin, azocyclotin, pyridaben, spirodiclofen, and etoxazole against adult T. urticae was 0.226, 0.240, 0.415, 3.583, 5.531, 25.58, 39.69, 140.3, and 267.7 mg/L, respectively. In addition, the LC50 value of the nine acaricides against eggs of T. urticae was 0.082, 0.097, 0.931, 18.56, 25.52, 45.61, 36.32, 1.954, and 0.040 mg/L, respectively. The field trial results showed that the best control effect was obtained in cyetpyrafen at 300 mL/ha treatment. Cyetpyrafen was chosen for further application technology tests. In the spray volume tests, the results showed that increasing the spray volume from 900 to 1050 L/ha significantly improved the control of T. urticae. In addition, the results from the spray instrument tests demonstrated that the control effects on T. urticae in the ozone spray treatments were significantly higher than those of the conventional and electrostatic sprays 1 and 3 days after treatment (DAT). Therefore, this study suggested that cyetpyrafen effectively controlled T. urticae both in the laboratory tests and in the field trials. Increasing the spray volume and application of ozone spray significantly improved T. urticae management.

Cooperative transcriptional regulation by ATAF1 and HY5 promotes light-induced cotyledon opening in Arabidopsis thaliana.

The opening of the embryonic leaves (cotyledons) as seedlings emerge from the dark soil into the light is crucial to ensure the survival of the plant. Seedlings that sprout in the dark elongate rapidly to reach light but keep their cotyledons closed. During de-etiolation, the transition from dark to light growth, elongation slows and the cotyledons open. Here, we report that the transcription factor ACTIVATING FACTOR1 (ATAF1) participates in de-etiolation and facilitates light-induced cotyledon opening. The transition from dark to light rapidly induced ATAF1 expression and ATAF1 accumulation in cotyledons. Seedlings lacking or overexpressing ATAF1 exhibited reduced or enhanced cotyledon opening, respectively, and transcriptomic analysis indicated that ATAF1 repressed the expression of genes associated with growth and cotyledon closure. The activation of the photoreceptor phytochrome A (phyA) by far-red light induced its association with the ATAF1 promoter and stimulation of ATAF1 expression. The transcription factor ELONGATED HYPOCOTYL5 (HY5), which is also activated in response far-red light, cooperated with phyA to induce ATAF1 expression. ATAF1 and HY5 interacted with one another and cooperatively repressed the expression of growth-promoting and cotyledon closure genes. Together, our study reveals a mechanism through which far-red light promotes cotyledon opening.

Novel dithiocarbamic acid esters derived from 6-aminomethyl-4-anilinoquinazolines and 6-aminomethyl-4-anilino-3-cyanoquinolines as potent EGFR inhibitors.

Two series of dithiocarbamic acid esters, 4-anilinoquinazoline-6-ylmethylcarbamodithioic acid esters and 3-cyano-4-anilinoquinolin-6-ylmethylcarbamodithioic acid esters, were designed and synthesized. The effect of the synthesized compounds on cell proliferation was evaluated by MTT assay against three human cancer cell lines: MDA-MB-468, SK-BR-3 and HCT-116. Most of the compounds are equally or more potent than the positive control lapatinib. Three compounds (14d, 14h and 14i) were identified as dual inhibitors of the EGFR and ErbB-2 kinases and two compounds (14b and 14c) were identified as multi-target kinase inhibitors, and they are very worthy of further study. Installation of the dithiocarbamic acid ester group at the 6-position of 4-anilinoquinazoline or 3-cyano-4-anilinoquinoline could improve the inhibitory activity. Different dithiocarbamic acid ester groups significantly affect the activities.

Oxidative stress and mitochondrial damage induced by a novel pesticide fluopimomide in Caenorhabditis elegans.

Fluopimomide is a novel pesticide intensively used in agricultural pest control; however, its excessive use may have toxicological effects on non-target organisms. In this study, Caenorhabditis elegans was used to evaluate the toxic effects of fluopimomide and its possible mechanisms. The effects of fluopimomide on the growth, pharyngeal pumping, and antioxidant systems of C. elegans were determined. Furthermore, the gene expression levels associated with mitochondria in the nematodes were also investigated. Results indicated that fluopimomide at 0.2, 1.0, and 5.0 mg/L notably (p < 0.001) decreased body length, pharyngeal pumping, and body bends in the nematodes compared to the untreated control. Additionally, fluopimomide at 0.2, 1.0, and 5.0 mg/L notably (p < 0.05) increased the content of malondialdehyde by 3.30-, 21.24-, and 33.57-fold, respectively, while fluopimomide at 1.0 and 5.0 mg/L significantly (p < 0.001) increased the levels of reactive oxygen species (ROS) by 49.14% and 77.06% compared to the untreated control. In contrast, fluopimomide at 1.0 and 5.0 mg/L notably reduced the activities of target enzyme succinate dehydrogenase and at 5.0 mg/L reduced the activities of antioxidant enzyme superoxide dismutase. Further evidence revealed that fluopimomide at 1.0 and 5.0 mg/L significantly inhibited oxygen consumption and at 0.2, 1.0, and 5.0 mg/L significantly inhibited ATP level in comparison to the untreated control. The expression of genes related to the mitochondrial electron transport chain mev-1 and isp-1 was significantly downregulated. ROS levels in the mev-1 and isp-1 mutants after fluopimomide treatments did not change significantly compared with the untreated mutants, suggesting that mev-1 and isp-1 may play critical roles in the toxicity induced by fluopimomide. Overall, the results demonstrate that oxidative stress and mitochondrial damage may be involved in toxicity of fluopimomide in C. elegans.

Mitochondrial alternative oxidase enhanced ABA-mediated drought tolerance in Solanum lycopersicum.

The phytohormone abscisic acid (ABA) plays essential roles in modulating drought stress responses. Mitochondrial alternative oxidase (AOX) is critical for reactive oxygen species (ROS) scavenging in drought stress responses. However, whether ABA signal in concert with AOX to moderate drought stress response remains largely unclear. In our study, we uncover the positive role of AOX in ABA-mediated drought tolerance in tomato (Solanum lycopersicum). Here, we report that ABA participates in the regulation of alternative respiration, and the increased AOX was found to improve drought tolerance by reducing total ROS accumulation. We also found that transcription factor ABA response element-binding factor 1 (SlAREB1) can directly bind to the promoter of AOX1a to activate its transcription. Virus-induced gene silencing (VIGS) of SlAREB1 compromised the ABA-induced alternative respiratory pathway, disrupted redox homeostasis and decreased plant resistance to drought stress, while overexpression of AOX1a in TRV2-SlAREB1 plants partially rescued the severe drought phenotype. Taken together, our results indicated that AOX1a plays an essential role in ABA-mediated drought tolerance partially in a SlAREB1-dependent manner, providing new insights into how ABA modulates ROS levels to cope with drought stress by AOX.