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

Abstract

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.