Comparative Study of the Abscisic Acid Metabolism Using Analogue Tritium-Labeled in the Cyclohexene or Side Moiety

© 2020, Pleiades Publishing, Ltd. Abstract: A procedure was developed for introducing tritium into the side chain of the abscisic acid (ABA) molecule. The reaction was carried out in dioxane in the presence of the Lindlar catalyst. The yield of the labeled product was 70% and the molar radioactivity was 44 Ci/mol. The tritium-labeled abscisic acid analogue was found to be a growth substrate for soil bacteria that incorporate a radioactive label into cellular metabolites. The absorption of the label by bacteria from the side chain of abscisic acid is more than an order of magnitude higher than that for labeling in the cyclohexene moiety. The results indicate the existence of a previously unknown metabolism pathway of ABA in microorganisms

Metabolism by Rhizobacteria of Abscisic Acid Deuterated in the Cyclohexene Part

The required amount of abscisic acid containing 4 – 5 D atoms ([2H]ABA) in the cyclohexene fragment of the molecule was produced via isotope exchange in 100% deuterated D2O at 220°C in the presence of diisopropyl ethylamine. The yield of labeled compound was 45 – 80%. A complex of biological studies was carried out using the D-labeled preparation. It was established that [2H]ABAserved as a growth substrate for soil bacteria, which included the isotopic label in the composition of cell metabolites. The characteristics of D-labeled metabolites allowed their reliable identification in mass spectra of the total bacterial metabolome. Three intermediates of a new metabolic pathway of microbial degradation of this phytohormone were identified using the developed technique

Rhizosphere bacterium rhodococcus sp. P1y metabolizes ab-scisic acid to form dehydrovomifoliol

The phytohormone abscisic acid (ABA) plays an important role in plant growth and in response to abiotic stress factors. At the same time, its accumulation in soil can negatively affect seed germination, inhibit root growth and increase plant sensitivity to pathogens. ABA is an inert compound resistant to spontaneous hydrolysis and its biological transformation is scarcely under-stood. Recently, the strain Rhodococcus sp. P1Y was described as a rhizosphere bacterium assimilat-ing ABA as a sole carbon source in batch culture and affecting ABA concentrations in plant roots. In this work, the intermediate product of ABA decomposition by this bacterium was isolated and purified by preparative HPLC techniques. Proof that this compound belongs to ABA derivatives was carried out by measuring the molar radioactivity of the conversion products of this phytohor-mone labeled with tritium. The chemical structure of this compound was determined by instrumen-tal techniques including high-resolution mass spectrometry, NMR spectrometry, FTIR and UV spec-troscopies. As a result, the metabolite was identified as (4RS)-4-hydroxy-3,5,5-trimethyl-4-[(E)-3-oxobut-1-enyl]cyclohex-2-en-1-one (dehydrovomifoliol). Based on the data obtained, it was con-cluded that the pathway of bacterial degradation and assimilation of ABA begins with a gradual shortening of the acyl part of the molecule