NO treatment of embryos isolated from artificially aged apple (Malus domestica Borkh.) seeds modifies the pattern of nitrated and carbonylated proteins.

Accelerated ageing of orthodox seeds of apple (Malus domestica Borkh.), resulting in loss of vigour, is associated with the overaccumulation of reactive oxygen species (ROS) and the depletion of reactive nitrogen species (RNS). Nitric oxide (NO) mitigates the detrimental effects of seed ageing. The aim of this work was to study the effects of NO treatment on the profile of proteins modified by ROS (carbonylated) and RNS (nitrated), in embryonic axes isolated from apple seeds artificially aged for 7, 14, and 21 days. We linked ageing-related deterioration in seeds with the activity of the protein quality control system: proteolytic degradation, ubiquitin-dependent and independent (20S) proteasome pathways. Various storage proteins underwent both carbonylation and nitration, which may be related to their signalling role. Most of the carbonylated proteins belonged to the late embryogenesis abundant (LEA) family. The carbonylation of heat shock protein (HSP) and seed biotin-containing protein (SBP) was also noted. Nearly all identified nitrated proteins were associated with energy generation, suggesting their impairment in seed ageing. NO treatment enhanced the activity of 20S proteasome in aged embryonic axes, revealing its role in protein degradation. Thus, we assume that NO mitigates the negative effects of seed ageing by partially alleviating embryo dormancy, activating its metabolism and stimulating the protein quality control system.