Gasotransmitters (NO and HCN) alter phytoglobin-NO cycle during dormancy alleviation of apple (Malus domestica Borkh.) embryos.

Nitric oxide (NO) and hydrogen cyanide (HCN) are N-containing gasotransmitters of bimodal action depending on the concentration. Both gases exhibit a beneficial effect on seed dormancy removal. The aim of this work was to compare the mode of action of NO and HCN on the elements of phytoglobin (Pgb)-NO cycle during seed dormancy alleviation (under aerobic conditions). Short-term fumigation of apple (Malus domestica Borkh.) embryos with HCN or NO increased the formation of reactive nitrogen species (RNS) in embryonic axes. The induction of nitrite/nitrate (NO2-/NO3-) signalling pathway, together with the increase of Pgb level and MetPgb reductase activity responsible for the regulation of NO concentration in the tissue, was observed. It was accompanied by a decrease in ATP content, which likely served as a signal for Pgb accumulation. The high content of NO2- in embryonic axes and the presence of NO2- in the culture medium may indicate a key role of these ions in the HCN and NO signalling pathway during seed dormancy breakage.