Molecular-genetic mechanisms of regulation of dihydroflavonol reductase and transcription factor Hy5 by exogenous 5-aminolevulinic acid in winter rape plants

The effect of exogenous 5-aminolevulinic acid (ALA) on the activity of dihydroflavonol-4-reductase (DFR), the expression of the dfr gene and the hy5 gene of the transcription factor Hy5 and the light effect of different intensities in combination with the ALA action on the accumulation of anthocyanins in cotyledonous leaves of winter rape (Brassica napus L.) were studied. It was shown that the stimulation of the accumulation of anthocyanins under the exogenous ALA action at the molecular level was provided by increasing the expression level of the dfr and hy5 genes and the activity of the DFR enzyme. Increasing the light intensity from 40.5 to 66.2 μmol photons/m²·s enhanced the ability of plants to accumulate anthocyanins on average by 35 %. The ALA action at concentrations of 50, 100, 150 and 200 mg/L led to an additional increase in the accumulation of anthocyanins at the two used levels of illumination, and in a dose-dependent manner. The stimulating effect of ALA under high light intensity was much higher than in the case of lower illumination. Thus, the stimulation of the anthocyanin accumulation under illumination of 40.5 μmol photons/m²·s was 106 % when using 50 mg/L ALA, 165 % – when using 100 mg/L ALA, 222 % – in the case of 150 mg/L ALA and 350 % – under the action of 200 mg/L ALA compared with light control without of ALA treatment. At an illumination of 66.2 μmol photons/m²·s, these indicators were 164, 262, 359 and 583 % respectively. Thus, it was demonstrated that the stimulation of the accumulation of anthocyanins under the action of ALA in winter rape plants was due to its positive effect on the transcription of the dfr and hy5 genes at the molecular level.

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