Effects of metribuzin herbicide on nitrogen,pigments, protease and nitrate reductase activity of normal and NaCl-stressed castor bean and maize plants

Addition of 0.5 and 2.5 gm^?3 of metribuzin into Hoagland nutrient media, either alone or in combination with NaCl, induced significant decreases in nitrate-, amino-, ammonia-, and total soluble-N contents, whereas significant increases in these nitrogen fractions were apparent in maize and castor bean seedlings and plants treated with high concentrations (5 and 10 g m^?3) of the herbicide, again either alone or in combination with NaCl. Protein- and total-N contents increased and decreased at low and high concentrations of the herbicide, respectively. The contents of chlorophyllsa andb, as well as carotenoids of both castor bean and maize seedlings and plants treated with low concentration of herbicide, either alone or supplemented with NaCl, were unaffected, whereas at high concentrations of the herbicide a significant decrease in chloroplast pigments was found. Nitrate reductase activity (NRA) was increased significantly at low concentrations of the herbicide alone and decreased significantly at high levels. Inclusion of NaCl into the herbicide media induced significant decreases in NRA of both castor bean and maize seedlings and plants. Unlike NRA changes, protease activity was increased significantly with high concentrations (5 and 10 g m^?3) of metribuzin and decreased significantly with its low (0.5 and 2.5 g m^?3) concentrations.     

Simultaneous assessment of the effects of an herbicide on the triad: rhizobacterial community, an herbicide degrading soil bacterium and their plant host

Aims

This work addresses the relevant effects that one single compound, used as model herbicide, provokes on the activity/survival of a suitable herbicide degrading model bacterium and on a plant that hosts this bacterium and its bacterial rhizospheric community.

Methods

The effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), on Acacia caven hosting the 2,4-D degrading bacterium Cupriavidus pinatubonensis JMP134, and its rhizospheric microbiota, were simultaneously addressed in plant soil microcosms, and followed by culture dependent and independent procedures, herbicide removal tests, bioprotection assays and use of encapsulated bacterial cells.

Results

The herbicide provokes deleterious effects on the plant, which are significantly diminished by the presence of the plant associated C. pinatubonensis, especially with encapsulated cells. This improvement correlated with increased 2,4-D degradation rates. The herbicide significantly changes the structure of the A. caven bacterial rhizospheric community; and it also diminishes the preference of C. pinatubonensis for the A. caven rhizosphere compared with the surrounding bulk soil.

Conclusions

The addition of an herbicide to soil triggers a complex, although more or less predictable, suite of effects on rhizobacterial communities, herbicide degrading bacteria and their plant hosts that should be taken into account in fundamental studies and design of bio(phyto)remediation procedures.     

Clomazone does not inhibit the conversion of isopentenyl pyrophosphate to geranyl, farnesyl, or geranylgeranyl pyrophosphate in vitro

Clomazone, an herbicide that reduces the levels of leaf carotenoids and chlorophylls, is thought to act by inhibiting isopentenyl pyrophosphate isomerase or the prenyltransferases responsible for the synthesis of geranylgeranyl pyrophosphate. Cell-free extracts prepared from the oil glands of common sage (Salvia officinalis) are capable of converting isopentenyl pyrophosphate to geranylgeranyl pyrophosphate. Clomazone at 250 micromolar (a level that produced leaf bleaching) had no detectable effect on the activity of the relevant enzymes (isopentenyl pyrophosphate isomerase and the three prenyltransferases, geranyl, farnesyl, and geranylgeranyl pyrophosphate synthases). Thus, inhibition of geranylgeranyl pyrophosphate biosynthesis does not appear to be the mode of action of this herbicide.     

Action de molecules a proprietes hormonales sur l'activite phenylalanine ammoniac lyase

A comparative study has been made of phenylalanine ammonia lyase (PAL) activity in plants sensitive or resistant to various herbicides (piclorame, methylchloro-phenoxyacetic acid (MCPA), atrazine). Piclorame, a herbicide with hormonal activity caused a large decrease in PAL activity of sensitive plants (Nicotiana tabacum), even at low concentrations (5 × 10^-9M) whilst in resistant plants (Triticum aestivum) its effect is negligible; MCPA, also a herbicide with hormonal activity, similarly affects the activity of PAL, but only at higher concentrations. On the contrary, the action of atrazine, which has no hormonal activity, is lower and weaker, probably being only a secondary effect. Determinations of PAL activity during the photoperiod following piclorame application indicate that this herbicide influences principally the photodependent enzyme activity.     

Genetic control of a cytochrome P450 metabolism-based herbicide resistance mechanism in Lolium rigidum

The dynamics of herbicide resistance evolution in plants are influenced by many factors, especially the biochemical and genetic basis of resistance. Herbicide resistance can be endowed by enhanced rates of herbicide metabolism because of the activity of cytochrome P450 enzymes, although in weedy plants the genetic control of cytochrome P450-endowed herbicide resistance is poorly understood. In this study we have examined the genetic control of P450 metabolism-based herbicide resistance in a well-characterized Lolium rigidum biotype. The phenotypic resistance segregation in herbicide resistant and susceptible parents, F1, F2 and backcross (BC) families was analyzed as plant survival following treatment with the chemically unrelated herbicides diclofop-methyl or chlorsulfuron. Dominance and nuclear gene inheritance was observed in F1 families when treated at the recommended field doses of both herbicides. The segregation values of P450 herbicide resistance phenotypic traits observed in F2 and BC families was consistent with resistance endowed by two additive genes in most cases. In obligate out-crossing species such as L. rigidum, herbicide selection can easily result in accumulation of resistance genes within individuals.     

Mechanism of Sulfonylurea Herbicide Resistance in the Broadleaf Weed, Kochia scoparia

Selection of kochia (Kochia scoparia) biotypes resistant to the sulfonylurea herbicide chlorsulfuron has occurred through the continued use of this herbicide in monoculture cereal-growing areas in the United States. The apparent sulfonylurea resistance observed in kochia was confirmed in greenhouse tests. Fresh and dry weight accumulation in the resistant kochia was 2- to >350-fold higher in the presence of four sulfonylurea herbicides as compared to the susceptible biotype. Acetolactate synthase (ALS) activity isolated from sulfonylurea-resistant kochia was less sensitive to inhibition by three classes of ALS-inhibiting herbicides, sulfonylureas, imidazolinones, and sulfonanilides. The decrease in ALS sensitivity to inhibition (as measured by the ratio of resistant I₅₀ to susceptible I₅₀) was 5- to 28-fold, 2- to 6-fold, and 20-fold for sulfonylurea herbicides, imidazolinone herbicides, and a sulfonanilide herbicide, respectively. No differences were observed in the ALS-specific activities or the rates of [¹⁴C]chlorsulfuron uptake, translocation, and metabolism between susceptible and resistant kochia biotypes. The K_m values for pyruvate using ALS from susceptible and resistant kochia were 2.13 and 1.74 mm, respectively. Based on these results, the mechanism of sulfonylurea resistance in this kochia biotype is due solely to a less sulfonylurea-sensitive ALS enzyme.     

Cytophysiological impacts of Metosulam herbicide on Vicia faba plants

The hazardous potential of the Metosulam herbicide, particularly the cytogenetic and physiological effects on Vicia faba cv Assuit 25 plants has been studied. The results showed that the mitotic index (MI) decreased and chromosomal aberrations frequency increased by increasing of the concentration of herbicide and prolonging the duration of treatment. In the roots treated with highest concentration used (1 × 10^?5 %) for 24 h, complete inhibition of cell division was observed. The chromosomal anomalies include chromosomal bridges and breaks that are regarded were indicative of a mutagenic potential of the herbicide. Seedling growth (fresh and dry weight) adversely affected as the duration and concentration of Metosulam herbicide increased. Soluble sugars, soluble proteins, total free amino acids and photosynthetic pigment content decreased significantly in root, stem and leaves of Vicia faba with increasing both the herbicide concentration and treatment duration. In contrast, proline content was highly accumulated, especially at the highest concentration (10^?4 %) and the longest duration used (24 h). The results of antioxidant enzymes reveal that while the peroxidase activity decreased by increasing the concentration of herbicide and duration, the activities of catalase and ascorbate peroxidase increased.     

In vitro synthesis, assembly and function of a photosynthetic membrane protein

Cell-free translation of Chlamydomonas reinhardtii RNA in the presence of photosynthetic membranes resulted in association of the herbicide binding (Qb) protein with membranes. Incubation of recovered membranes with high salt did not extract the polypeptide from membranes. Tryptic digestion of in vivo labeled membranes or membranes recovered from in vitro translation mixtures showed that Qb had similar orientation. In vitro translation in the presence of chloroplast membranes from cells exposed to high light intensity restored the membrane associated kinase activity lost by photoinhibition. Thus, in vitro synthesis resulted in functional integration of the Qb protein within the photosynthetic membrane.     

Resistance to Acetolactate Synthase-Inhibiting Herbicides in Annual Ryegrass (Lolium rigidum) Involves at Least Two Mechanisms

WLR1, a biotype of Lolium rigidum Gaud. that had been treated with the sulfonylurea herbicide chlorsulfuron in 7 consecutive years, was found to be resistant to both the wheat-selective and the nonselective sulfonylurea and imidazolinone herbicides. Biotype SLR31, which became cross-resistant to chlorsulfuron following treatment with the aryloxyphenoxypropionate herbicide diclofop-methyl, was resistant to the wheat-selective, but not the nonselective, sulfonylurea and imidazolinone herbicides. The concentrations of herbicide required to reduce in vitro acetolactate synthase (ALs) activity 50% with respect to control assays minus herbicide for biotype WLR1 was greater than those for susceptible biotype VLR1 by a factor of >30, >30, 7,4, and 2 for the herbicides chlorsulfuron, sulfometuron-methyl, imazapyr, imazathapyr, and imazamethabenz, respectively. ALS activity from biotype SLR31 responded in a similar manner to that of the susceptible biotype VLR1. The resistant biotypes metabolized chlorsulfuron more rapidly than the susceptible biotype. Metabolism of 50% of [phenyl-U-¹⁴C]chlorsulfuron in the culms of two-leaf seedlings required 3.7 h in biotype SLR31, 5.1 h in biotype WLR1, and 7.1 h in biotype VLR1. In all biotypes the metabolism of chlorsulfuron in the culms was more rapid than that in the leaf lamina. Resistance to ALS inhibitors in L. rigidum may involve at least two mechanisms, increased metabolism of the herbicide and/or a herbicide-insensitive ALS.     

Responses of soil nitrogen-fixing, ammonia-oxidizing, and denitrifying bacterial communities to long-term chlorimuron-ethyl stress in a continuously cropped soybean field in Northeast China

Chlorimuron-ethyl is a type of long-residual herbicide applied widely to soybean fields in China, but little information is available about the long-term impact of this herbicide on soil nitrogen-transforming microbial communities. Soil samples (0–20 cm) were collected from three treatments (no, 5-year and 10-year application of chlorimuron-ethyl) in a continuously cropped soybean field. Plate count (CFU), most probable number (MPN) count, and clone library analyses were conducted to investigate the abundance and composition of nitrogen-fixing, ammonia-oxidizing, and denitrifying bacterial communities, and a chlorate inhibition method was adopted to measure the soil nitrification potential. Long-term chlorimuron-ethyl application reduced the abundance of soil culturable nitrogen-fixing, ammonia-oxidizing, and denitrifying bacteria. Moreover, chlorimuron-ethyl decreased the diversity of nitrogen-fixing and ammonia-oxidizing bacteria but promoted that of denitrifying bacteria. Chlorimuron-ethyl restrained some uncultured nitrogen-fixing bacteria, ammonia-oxidizing bacteria Nitrosospira sp. cluster 3a and 3d, and some novel or putative denitrifying bacteria. The nitrogen-fixing bacteria were closely related to Bradyrhizobium sp., ammonia-oxidizing bacteria Nitrosospira sp. cluster 3b and 3c, and most denitrifying bacteria were resistant to chlorimuron-ethyl. There was a negative correlation between the nitrification potential and the residual amount of soil chlorimuron-ethyl (R²?=?0.88, n?=?3, P?<?0.05). Therefore, long-term application of chlorimuron-ethyl in the continuously cropped soybean field could seriously disturb soil N-transforming communities, and might impact soybean soil biological quality and soybean growth. Further studies should address rational amendment models of this herbicide to reduce the possible ecological risks of long-term application of this herbicide to soybean fields.     

Effects of Acifluorfen on Endogenous Antioxidants and Protective Enzymes in Cucumber (Cucumis sativus L.) Cotyledons

The herbicide acifluorfen (2-chloro-4-(trifluoromethyl)phenoxy-2-nitrobenzoate) causes strong photooxidative destruction of pigments and lipids in sensitive plant species. Antioxidants and oxygen radical scavengers slow the bleaching action of the herbicide. The effect of acifluorfen on glutathione and ascorbate levels in cucumber (Cucumis sativus L.) cotyledon discs was investigated to assess the relationship between herbicide activity and endogenous antioxidants. Acifluorfen decreased the levels of glutathione and ascorbate over 50% in discs exposed to less than 1.5 hours of white light (450 microeinsteins per square meter per second). Coincident increases in dehydroascorbate and glutathione disulfide were not observed. Acifluorfen also caused the rapid depletion of ascorbate in far-red light grown plants which were photosynthetically incompetent.

Glutathione reductase, dehydroascorbate reductase, superoxide dismutase, ascorbate oxidase, ascorbate free radical reductase, peroxidase, and catalase activities rapidly decreased in acifluorfen-treated tissue exposed to white light. None of the enzymes were inhibited in vitro by the herbicide. Acifluorfen causes irreversible photooxidative destruction of plant tissue, in part, by depleting endogenous antioxidants and inhibiting the activities of protective enzymes.

     

Nitrogen Fixation by Photosynthetic Bacteria in Lowland Rice Culture

Propanil (3′,4′-dichloropropionanilide) was a potent inhibitor of the nitrogenase activity of blue-green algae (cyanobacteria) in flooded soil, but the herbicide at comparable concentrations was not toxic to rice, protozoa, and nitrogen-fixing bacteria. Ethanol-amended flooded soils treated with propanil exhibited higher rates of nitrogenase activity than those not treated with the herbicide. The enhanced nitrogenase activity in propanil-treated soils was associated with a rise in the population of purple sulfur bacteria, especially of cells resembling Chromatium and Thiospirillum. By employing propanil and a means of excluding light from the floodwater to prevent the development of phototrophs during rice growth under lowland conditions, the relative activities of blue-green algae, photosynthetic bacteria, and the rhizosphere microflora were determined. The results suggest that the potential contribution of photosynthetic bacteria may be quite high.     

Photosynthesis of soybean under the action of a photosystem II-inhibiting herbicide

Photosynthesis, the fundamental physiological process of plant responsible for the growth and yield of crops, is strongly affected by environmental stresses. Several methods have been used to study changes in the physiological parameters of plants exposed to stresses. The work aimed to study physiological parameters related to photosynthesis in leaf discs of soybean plants exposed to a photosystem II-inhibiting herbicide. Soybean leaf discs obtained from mature leaves of plants in the vegetative stage immersed in bentazon herbicide solutions at concentrations of 0, 100, 250 or 500 μM were evaluated. In experiment I, the effect of the herbicide on chlorophyll a fluorescence transient was measured using a portable fluorometer. In the second experiment, the effect of the herbicide on modulated chlorophyll a fluorescence and gas exchange were evaluated, with the latter being measured with an infrared gas analyzer. The evaluations of transient and modulated fluorescence provided additional information on the photosynthetic activity of soybean leaf discs exposed to the action of bentazon. For the fluorescence transient analysis, performance indices were the parameters most sensitive to the action of bentazon, showing a decrease of approximately 70 % at a dose of 500 μM. For the modulated fluorescence analysis, the photochemical quenching coefficient, the electron transport rate, the photochemical efficiency of photosystem II and the net assimilation rate, decreased in response to herbicide application, with values that were almost equal to zero at a dose of 500 µM, which are the parameters that showed the greatest sensitivity to bentazon in soybean.     

Isolation and characterization of a glyphosate-degrading rhizosphere strain,Enterobacter cloacae K7

Plant-growth-promoting rhizobacteria exert beneficial effects on plants through their capacity for nitrogen fixation, phytohormone production, phosphate solubilization, and improvement of the water and mineral status of plants. We suggested that these bacteria may also have the potential to express degradative activity toward glyphosate, a commonly used organophosphorus herbicide. In this study, 10 strains resistant to a 10 mM concentration of glyphosate were isolated from the rhizoplane of various plants. Five of these strains – Alcaligenes sp. K1, Comamonas sp. K4, Azomonas sp. K5, Pseudomonas sp. K3, and Enterobacter cloacae K7 – possessed a number of associative traits, including fixation of atmospheric nitrogen, solubilization of phosphates, and synthesis of the phytohormone indole-3-acetic acid. One strain, E. cloacae K7, could utilize glyphosate as a source of P. Gas–liquid chromatography showed that E. cloacae growth correlated with a decline in herbicide content in the culture medium (40% of the initial 5 mM content), with no glyphosate accumulating inside the cells. Thin-layer chromatography analysis of the intermediate metabolites of glyphosate degradation found that E. cloacae K7 had a C–P lyase activity and degraded glyphosate to give sarcosine, which was then oxidized to glycine. In addition, strain K7 colonized the roots of common sunflower (Helianthus annuus L.) and sugar sorghum (Sorghum saccharatum Pers.), promoting the growth and development of sunflower seedlings. Our findings extend current knowledge of glyphosate-degrading rhizosphere bacteria and may be useful for developing a biotechnology for the cleanup and restoration of glyphosate-polluted soils.     

Developmental Effects of Sandoz 6706 on Activities of Enzymes of Phenolic and General Metabolism in Barley Shoots Grown in the Dark or under Low or High Intensity Light

The activities of three enzymes of phenolic biosynthesis and six of general metabolism were studied at 24-hour intervals between the 3rd and 8th day after planting in barley shoots treated with the chlorosis-inducing herbicide Sandoz 6706 and grown in the dark or under high or low intensity light. The herbicide had no effect on fresh weight or soluble protein (per shoot) in plants grown in the dark or under low intensity light, but slightly decreased these parameters in plants grown for more than 5 days under high intensity light. In dark-grown seedlings the herbicide had no detectable effects on plastid ultrastructure or on the activity of malate dehydrogenase, cytochrome c oxidase, NADP-cytochrome c reductase, triose phosphate isomerase, peroxidase, catalase, shikimate dehydrogenase, phenylalanine ammonia-lyase, or chalcone-flavanone isomerase. Under low intensity light, Sandoz 6706-treated plants developed plastids with single thylakoids extending across the organelle, and the activity of all enzymes examined was increased to varying degrees. When the herbicide-treated plants were grown under high intensity light, plastid lamellar organization was severely disrupted. Activities of shikimate dehydrogenase and chalcone-flavanone isomerase were markedly enhanced, phenylalanine ammonia-lyase activity slightly promoted, and catalase activity severely inhibited. The other enzymes were not appreciably affected by Sandoz 6706 under high intensity light. It is concluded that the changes in plastid ultrastructure and enzyme activities of the herbicide-treated plants are largely secondary photomorphogenetic or photooxidative responses in the carotenoid-free plants in which chlorophylls accumulate in reduced amounts (low intensity light) or are completely absent (high intensity light).     

Synthesis and biological evaluation of arylhydrazinocyanoacrylates and N-aryl pyrazolecarboxylates

A series of arylhydrazino-substituted cyanoacrylates 3 and N-aryl pyrazolecarboxylates 6 were synthesized and their bioactivities were evaluated. Though compounds 3 were designed as herbicide, some of them showed fungicidal activity and anti-tumor activity. Some of the compounds 6 exhibited plant growth regulatory activity.     

Focus on Weed Control: A Novel Rice Cytochrome P450 Gene,CYP72A31, Confers Tolerance to Acetolactate Synthase-Inhibiting Herbicides in Rice and Arabidopsis

Target-site and non-target-site herbicide tolerance are caused by the prevention of herbicide binding to the target enzyme and the reduction to a nonlethal dose of herbicide reaching the target enzyme, respectively. There is little information on the molecular mechanisms involved in non-target-site herbicide tolerance, although it poses the greater threat in the evolution of herbicide-resistant weeds and could potentially be useful for the production of herbicide-tolerant crops because it is often involved in tolerance to multiherbicides. Bispyribac sodium (BS) is an herbicide that inhibits the activity of acetolactate synthase. Rice (Oryza sativa) of the indica variety show BS tolerance, while japonica rice varieties are BS sensitive. Map-based cloning and complementation tests revealed that a novel cytochrome P450 monooxygenase, CYP72A31, is involved in BS tolerance. Interestingly, BS tolerance was correlated with CYP72A31 messenger RNA levels in transgenic plants of rice and Arabidopsis (Arabidopsis thaliana). Moreover, Arabidopsis overexpressing CYP72A31 showed tolerance to bensulfuron-methyl (BSM), which belongs to a different class of acetolactate synthase-inhibiting herbicides, suggesting that CYP72A31 can metabolize BS and BSM to a compound with reduced phytotoxicity. On the other hand, we showed that the cytochrome P450 monooxygenase CYP81A6, which has been reported to confer BSM tolerance, is barely involved, if at all, in BS tolerance, suggesting that the CYP72A31 enzyme has different herbicide specificities compared with CYP81A6. Thus, the CYP72A31 gene is a potentially useful genetic resource in the fields of weed control, herbicide development, and molecular breeding in a broad range of crop species.The mechanism of herbicide tolerance can be classified roughly into two groups: target-site and non-target-site herbicide tolerance (Powles and Yu, 2010). Target-site herbicide tolerance is caused by the prevention of herbicide binding to the target enzyme, caused by point mutations occurring in the latter. It is relatively easy to elucidate the molecular mechanisms of target-site herbicide tolerance, because it is regulated mostly by a single gene encoding a target enzyme harboring point mutations. On the other hand, non-target-site herbicide tolerance is caused by reduction to a nonlethal dose of herbicide reaching the target enzyme, caused by mechanisms such as activation of herbicide detoxification, decrease of herbicide penetration, and herbicide compartmentation in plant cells (Yuan et al., 2007). Among these mechanisms, the oxidization of herbicides by endogenous cytochrome P450 monooxygenase is thought to be a major pathway in plants (Werck-Reichhart et al., 2000; Siminszky, 2006; Powles and Yu, 2010). From the point of view of weed control, non-target-site herbicide tolerance is a greater threat to crop production and in the evolution of herbicide-resistant weeds, because it is often involved in resistance to multiherbicides that inhibit different target proteins, including never-used and potential plant growth regulators (Yuan et al., 2007; Powles and Yu, 2010). Conversely, it is expected that multiherbicide-tolerant crops could be produced easily by the application of non-target-site herbicide tolerance. Moreover, information gained from study of the molecular mechanisms of non-target-site herbicide tolerance can be applied to the research and development of novel herbicides and plant growth regulators.Acetolactate synthase (ALS; also known as acetohydroxy acid synthase) plays a key role in the biosynthesis of branched-chain amino acids such as Val, Leu, and Ile in many organisms. ALS is the primary target site for at least four classes of herbicides: sulfonylurea, imidazolinone, pyrimidinyl carboxylates, and triazolopyrimidine herbicides (Shimizu et al., 2002, 2005). These herbicides can inhibit ALS activity, resulting in plant death caused by a deficiency of branched-chain amino acids. ALS-inhibiting herbicides control many weed species in addition to exhibiting high selectivity in major crops and low toxicity to mammals, which lack the branched-chain amino acid biosynthetic pathway. However, various mutations in ALS that confer ALS-inhibiting herbicide tolerance have been found in many weeds (Shimizu et al., 2005; Powles and Yu, 2010). Similar mutations in ALS have also been reported in crops (Shimizu et al., 2005). To date, crops that show tolerance to ALS-inhibiting herbicides have been produced by various approaches, such as conventional mutation breeding, conventional transformation, and pinpoint mutagenesis via gene targeting based on information obtained from analyses of ALS mutants (Shimizu et al., 2005; Endo and Toki, 2013). On the other hand, weeds that show tolerance to ALS-inhibiting herbicides by cytochrome P450-mediated detoxification have also been reported (Powles and Yu, 2010). However, compared with target-site herbicide tolerance, little is known of the molecular mechanism of herbicide metabolism mediated by cytochrome P450. In rice (Oryza sativa), an herbicide-sensitive mutant has been produced by γ-ray irradiation (Zhang et al., 2002). This mutant showed 60-fold higher sensitivity to bensulfuron-methyl (BSM), a sulfonylurea herbicide, compared with wild-type rice (Pan et al., 2006). Genetic mapping and complementation tests revealed that a cytochrome P450, CYP81A6, is involved in BSM tolerance (Pan et al., 2006). As far as we know, this is the only example of the isolation and characterization of a cytochrome P450 gene involved in nontarget herbicide tolerance in rice.Bispyribac sodium (BS), a pyrimidinyl carboxylate herbicide, is effective in controlling many annual and perennial weeds, with excellent selectivity on direct-seeded rice (Shimizu et al., 2002). Recently, it was reported that japonica rice varieties show higher sensitivity to BS compared with indica rice varieties at the early stages of plant growth (Ohno et al., 2008; Taniguchi et al., 2010). A mutated ALS gene confers BS tolerance in plants including rice (Shimizu et al., 2005; Endo and Toki, 2013). However, the deduced amino acid sequences were shown to be highly conserved among japonica and indica rice varieties, and ALS levels of sensitivity to BS were similar in japonica and indica rice varieties (Taniguchi et al., 2010). These results suggest the possibility that indica rice varieties might show higher tolerance to BS due to the acquisition of nontarget herbicide tolerance.In this study, we isolated and characterized a novel cytochrome P450 gene, CYP72A31, involved in BS tolerance in rice. We also demonstrated that overexpression of CYP72A31 confers tolerance to ALS-inhibiting herbicides, including BS and BSM, in Arabidopsis (Arabidopsis thaliana).     

Effect of boric acid on antioxidant enzyme activity, lipid peroxidation, and ultrastructure of midgut and fat body of Galleria mellonella

Boric acid is widely used as an insecticide, acaricide, herbicide, and fungicide and also during various industrial processings. Hence, numerous populations are subjects to this toxic compound. Its action on animals is still not fully known and understood. We examined the effect of boric acid on larvae of greater wax moth (Galleria mellonella). The chemical appeared to be toxic for larvae, usually in a concentration-dependent manner. Exposed groups revealed increased lipid peroxidation and altered activity of catalase, superoxide dismutase, glutathione S-transferase, and glutathione peroxidase. We also observed changes of ultrastructure, which were in tune with biochemical assays. We suggest that boric acid has a broad mode of action, which may affect exposed larvae, and even if sublethal, they may lead to disturbances within exposed populations.