We compared the responses of superoxide dismutase (SOD) and catalase (CAT) to a herbicide norflurazon (NF)-induced oxidative stress in leaves and mesocotyls of a standard maize (Zea mays) inbred line (W64A) to those of a SOD mutant (A130-1) having a mutation in Sod1. The changes in activities of SOD and CAT with NF treatment did not differ between W64A and A130-1. The relative transcript levels of Sod1 and Cat1 increased greatly in response to NF in leaves and mesocotyls of the two maize lines. In leaf and mesocotyl tissues, the Sod3 transcript increased only at a 33 μM NF in W64A, whereas Sod3 increased at 33 μM and 100 μM in A130-1. The Sod4A transcript increased only in mesocotyls of NF-treated A130-1, but the total Sod4A transcript level was much higher in W64A than in A130-1. Cat2 increased in the leaves of NF-treated W64A but decreased significantly in the leaves of A130-1. In mesocotyls, the Cat2 transcript increased only in A130-1 upon NF treatment. The maize variant with a mutation in Sod1 demonstrated differences in the induction of Sod and Cat transcripts from the standard inbred line W64A in response to NF-induced oxidative stress.

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The effect of catalase (CAT) levels on antioxidant responses to norflurazon (NF)-induced photooxidative stress was examined in 5-day postimbibition (dpi) scutella of a standard maize (Zea mays) CAT line (W64A) and various CAT mutants. In W64A and CAT-3 null (WI10D), CAT activities decreased at 1 μM NF and increased at 10 μM NF. The CAT activities of CAT-2 null (WA10C) and CAT-2/CAT-3 double null (WDN10) were very low throughout all treatments. The high CAT-2 activity mutant (R6-67) had decreased CAT activity but maintained the highest level among the various CAT lines upon NF treatment, and also had the highest level of SOD activity. Total SOD activity and SOD isozyme patterns were relatively consistent at NF concentrations of 1-10 μM in scutella of all maize CAT lines examined. The mutants lacking the CAT isozyme were capable of maintaining a high level of SOD in response to NF, demonstrating that SOD is the base-level scavenger of NF-mediated photooxidative stress. An increase in Cat1, Cat2, and Cat3 transcript levels occurred in scutella of R6-67, but not W64A following treatment with NF. All Sod transcript levels except the level of Sod1 responded differentially between NF-treated scutella of W64A and R6-67. W64A and maize mutant line expressing strong CAT-2 activity exhibited a different response to NF at the protein and mRNA levels of CAT and SOD. These results indicate that the level of a specific CAT isozyme in the maize mutants affects the levels of CAT and SOD.

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A series of 3(2H)-oxo-N-(substituted phenyl)-4,5,6,7-tetrahydro-1,2-benzisothiazoles (2) were obtained via four reaction steps starting from 2-chlorocyclohexene-1-carboxylic acid. The sulfur atom of 3-oxo-4,5,6,7-tetrahydro-1,2-benzisothiazoles (2) was oxidized with an equimolecular amount of 3-chloroperbenzoic acid (3-CPBA) in chloroform to give the corresponding 3-oxo-4,5,6,7-tetrahydro-1,2-benzisothiazole-1-oxides (3). Oxidation of 2 with two moles of 3-CPBA afforded 3-oxo-4,5,6,7-tetrahydro-1,2-benzisothiazole-1,1-dioxides (4). Phytotoxic activities of the compounds (2-4) synthesized were assayed by inhibition of protoporphyrinogen-IX oxidase isolated from corn as well as by growth inhibition, chlorophyll decrease and peroxidative destruction of cell membranes of the green microalga Scenedesmus acutus. Among the compounds (2-4), 4 showed the strongest activities according to all phytotoxic parameters, exhibiting phytotoxicities characteristic of peroxidizing herbicides. 3(2H)-oxo-2-[4-chloro-3-(isopropoxycarbonyl)phenyl]-4,5,6,7-tetrahydro-1,2-benzisothiazole-1,1-dioxide (4h) was the strongest of the compounds 4 tested.

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When mice were immunized with the conjugate EIT244-KLH containing malathion-hapten with a P-NH-C instead of P-S-C bond, two monoclonal antibodies (mabs) MLT2-23 and MLT40-4 specific to the insecticide malathion were isolated and characterized in a direct competitive enzyme-linked immunosorbent assay (dc-ELISA). Other haptens with the P-S-C bond failed to raise antibodies against malathion. Malathion was determined in the ranges of 5.3 to 75 ng/ml and of 7.0 to 190 ng/ml in a dc-ELISA based on the mabs MLT2-23 and MLT40-4, respectively. Then, cDNA clones encoding heavy chain and light chain regions of both mabs were isolated from two individual cDNA libraries constructed from mRNA fractions extracted from hybridoma cells producing the corresponding mabs. Two types of single-chain variable fragment (scFv) antibody genes with the sequences of VH-linker-VL (HL) and VL-linker-VH (LH), respectively, were constructed on the basis of the cDNA clones of each mab, inserted into the phagemid vector pCANTAB5E and expressed in Escherichia coli HB2151 cells. The IC₅₀ in an indirect competitive ELISA (ic-ELISA) with MLT2-23/HL scFv and MLT2-23/LH scFv for malathion was 81 ng/ml and 72 ng/ml, respectively, compared to 60 ng/ml with the parent mab MLT2-23. On the other hand, MLT40-4/LH scFv showed an IC₅₀ value of 150 ng/ml, in contrast to 75 ng/ml with the parent mab MLT40-4, while MLT40-4/HL scFv hardly reacted at all with malathion in the ic-ELISA. It was found that the order of linkage of both VL and VH allowed the scFv antibodies to alter their antigen-binding affinity or antigen-antibody reactivity in the case of MLT40-4 scFvs.

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Very-long-chain fatty acids (VLCFAs) having more than 18 C-atoms (like C20, 22, 24) are formed by a microsomal elongase system of the endoplasmic reticulum. This 4-step catalytic system is strongly inhibited by chloroacetamides with I₅₀-values of 10 to 100 nM. Inhibition depends on the amide structure and on stereospecificity (for e.g. metolachlor). Also structures different from chloroacetamides like cafenstrole or fentrazamide (a tetrazolinone) exhibit strong inhibitory activity. A cell-free assay was developed using isolated microsomes from Allium porrum (leek) with labeled malonyl-CoA and C18, C20 or C22 acyl-CoA as primer substrates. All elongation steps were strongly inhibited by those phytotoxic compounds which also have been found active in the intact plant. While the plant contains in total about 1% VLCFAs, the plasma membrane (plasmalemma) is enriched. Isolated plasma membranes (from cucumber) have a small VLCFA content when treating the intact plant with the herbicides. There is evidence that such membrane looses its stability and function, and we conclude that herbicidal phytotoxicity is correlated with a non-balanced VLCFA pattern. Data with transformed yeast demonstrate that the key target for chloroacetamides is exclusively the condensing starter enzyme (=VLCFA synthase) of the elongase system. An irreversible binding complex of synthase and inhibitor is assumed. Reports in literature indicate that flavonoid and anthocyanin biosynthesis is affected by chloroacetamides. Since it was speculated that this inhibition may cause plant death chalcone synthase was assayed catalyzing the key condensing reaction between malonyl-CoA and coumaroyl-CoA. Also this enzyme was inhibited by chloroacetamides or cafenstrole. Our enzymological studies, however, could demonstrate that this inhibition does not cause the herbicidal effect. — Based on our recent findings a reasoning is presented why resistance of weeds against this class of herbicides is a rare event.

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The effect of three-stage spraying of 200 mg/l ethephon in the flower bud stage with leaf primordium and involucre was studied for chemical control of growth and flowering in summer-to-autumn-flowering chrysanthemum (Dendranthema grandiflorum (Ramat.) Kitamura) cultivars under open field conditions. Leaf primordium and young leaf numbers of ‘Iwanohakusen’,‘Madobe’,‘Seiun’ and ‘Summer-yellow’ with and without ethephon spraying were 17.3–18.2 in the early growing stage, and maximum leaf primordium and young leaf numbers were 19.8–22.8 in the starting involucre formation stage, and decreased after that. The development of leaf primordium and young leaf numbers under ethephon spraying was inhibited by 15–30 days compared to without ethephon. Leaf primordium development and young leaf numbers of ‘Summer-yellow’ with ethephon were more inhibited than other cultivars. The budding was also markedly inhibited and the leaf numbers were increased. As a result, the transformation from leaf primordium to involucre was inhibited by ethephon application in summer-to-autumn-flowering chrysanthemum.

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