Inhibition of Plant Acetolactate Synthase by Herbicides, Pyrimidinylsalicylic Acids

Abstract

The growth inhibition of rice seedlings and chlorella by the herbicides, pyrimidinylsalicylic acids (PSs) represented by pyrithiobac (2-chloro-6-(4, 6-dimethoxypyrimidine-2ylthio)benzoic acid) was alleviated almost completely by simultaneous application of three branched-chain amino acids, namely leucine, valine and isoleucine. PS's inhibited potently acetolactate synthase (EC 4. 1.3. 18) in various species of plants including crops and weeds, which catalyzes the condensation step of two molecules of pyruvate to form acetolactate in the biosynthetic pathway of branched-chain amino acids. PS's, however, affected neither ketol-acid reductoisomerase which catalyzes the next reaction step from acetolactate synthase in the pathway nor direct acetoin forming enzyme deduced as pyruvate decarboxylase. PS's showed no inhibitory effect on photosynthetic electron transport system of pea, while they inhibited slightly chlorophyll biosynthesis of cotton cotyledons. In spite of high selectivity of pyrithiobac for cotton plants, there was no difference in sensitivity of ALS to pyrithiobac between cotton and other plants.

Cool-Season Turfgrass Reseeding Intervals for Bispyribac-Sodium

“…ALS-inhibiting herbicides block formation of the branched-chain amino acids leucine, isoleucine, and valine within a susceptible plant (Shimizu et al 1994). Bispyribac is registered for selective postemergence control of annual bluegrass (Poa annua L.) and roughstalk bluegrass (Poa trivialis L.) in creeping bentgrass and perennial ryegrass golf course fairways or sod farms (Anonymous 2004).…”

Partial Purification and Properties of Acetolactate Synthase of Etiolated Pea Seedlings

“…But, that of etiolated pea seedlings was due to the chemical decarboxylation of acetolactate which was produced from pyruvate by ALS, while that of germinated pea seeds were attributable to pyruvate decarboxylase which catalyzes the direct acetoin formation by pyruvate as its side reaction. 22,27 No activities of acetolactate decarboxvlase were found in both the crude enzymes of etiolated seedlings and germinated seeds of pea.…”

“…Akabanatsurunashi) by the method reported previously. 22) 3. Purification of ALS from Etiolated Pea Seedlings ALS was extracted from 5-to 7-day-old etiolated pea shoots which were grown under dark at 27°C.…”

A facile synthesis of [14C]pyrithiobac‐sodium

“…It inhibits the synthesis of the essential branched chain amino acids (leucine, iso-leucine and valine). [1][2][3] This herbicide acts against a broad spectrum of weeds associated with the cotton crop. It is used at low rates, as soil or foliar applied, at both pre-and post-emergence stages of the cotton crop.…”