Signaling by glutamate dehydrogenase in response to pesticide treatment and nitrogen fertilization of peanut (Arachis hypogaea L.)

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Journal of Agricultural and Food Chemistry


The responses of glutamate dehydrogenase (GDH) to NH4+ and herbicides offer a new approach for probing the effects of NH4+-pesticide interactions at the whole-plant level. Although pesticides and fertilizers have greatly enhanced food production, their combined biochemical effects are not known in detail. Peanut plants were treated with different rates of Basagran (3-(1- methylethyl)1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide), Bravo 720 (tetrachloroiso-phthalonitrile), and Sevin XLR Plus (1-naphthyl N- methylcarbamate), with and without 25 mM NH4Cl fertilization. Isoelectric focusing, followed by native 7.5% polyacrylamide gel electrophoresis (PAGE) fractionated the peanut seed GDH fully to its isoenzyme population patterns. The pesticide treatments induced positive skewing of the GDH isoenzymes, but NH4Cl-pesticide cotreatments induced a negatively skewed distribution. Basagran, Sevin, and Bravo increased the amination activities of GDH from 30.0 ± 2.8 units in the control assay to 479.0 ± 20.7, 63.0 ± 5.8, and 35.2 ± 2.2 units, respectively, therefore indicating a direct GDH-pesticide interaction. Neither the NH4+ nor the pesticides increased the peanut seed protein yields above the threshold of 3.8 ± 0.7 g per pot. But in the GDH combination of the signals from a pesticide and NH4+, at least 70% of the pesticide signal was overridden by NH4+ with concomitant increases in peanut seed protein yields to 7.0 ± 1.8 g per pot. Basagran, Sevin, and Bravo possess different pesticidal properties, but their effects on GDH activity were related in the decreasing order of their nucleophilicity, viz. Basagran > Sevin > Bravo.

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