Stress responses of tomato fruit tissue submitted to massive doses of ionising radiation

Abstract

AbstractIn plant tissue, massive doses of ionising radiation (0.5–3 kGy) induce an oxidative burst due to the overproduction of oxygen-centred free radicals. Changes in the protein metabolism of cherry tomato fruits were investigated in response to this peculiar stress. Although DNA damage definitively arrested cell division, the changes observed on a short-term basis were attributed to genetic regulation. Changes in protein metabolism were also maintained long term. Gamma-induced proteins (GIPs) were classified according to their induction kinetics. Group 1 proteins were induced immediately after the treatment and their synthesis was stopped within 24 h. During the same time period, global protein synthesis was restored and a new set of GIPs was induced. The function of these proteins is not yet known; but they may be involved in physiological disorders triggered by irradiation or in repair processes. Short-term typical changes involve the synthesis of ACC synthase – the ethylene pathway regulating enzyme - and most probably of some LMW-HSPs. A non-relevant response to irradiation has also been discovered, namely the long-term accumulation of chitinases. Irradiation induces both specific and non-specific responses which can be analysed by comparison with other types of oxidative stress and some GIPs seem to be specific to the treatment. The ability of irradiation to induce such different responses might be profitably applied for a better understanding of the oxidative mechanisms involved in signal transduction during environmental stress situations.