Regulation of lipoxygenase gene expression in potato mini-tubers by phytohormones

The effects of phytohormones on the activity of lipoxygenase (LOX) and the content of 9-LOX mRNAs in potato (Solanum tuberosum L., cv. Odissei) mini-tubers were studied in model (incubation of disks cut from mini-tubers on phytohormone solutions) and vegetation (spraying with phytohormone solutions at various developmental stages) experiments. In model experiment, it was shown that most tested phytohormones (auxin, kinetin, epibrassinolide, gibberellin, and salicylic acid) suppressed LOX activity. At the same time, auxin and gibberellin increased the amount of 9-LOX gene transcripts, whereas other phytohormones reduced it. Under conditions of vegetation experiment, principal differences between auxin and kinetin action were revealed. In both types of experiments, kinetin affected similarly both LOX activity and the amount of 9-LOX transcripts. In the case of auxin treatments, opposite situation was observed: the highest content of 9-LOX gene transcripts corresponded to the lowest enzyme activity. The results obtained show a great phytohormone influence on different stages of 9-LOX gene expression. Kinetin affected enzyme activity via its effect on the level of transcription, whereas auxin controls LOX activity on another level, although it affects the content of transcripts as well.