Understanding the role of H(2)O(2) during pea seed germination: a combined proteomic and hormone profiling approach

In a previous publication, we showed that the treatment of pea seeds in the presence of hydrogen peroxide (H(2)O(2)) increased germination performance as well as seedling growth. To gain insight into the mechanisms responsible for this behaviour, we have analysed the effect of treating mature pea seeds in the presence of 20 mm H(2)O(2) on several oxidative features such as protein carbonylation, endogenous H(2)O(2) and lipid peroxidation levels. We report that H(2)O(2) treatment of the pea seeds increased their endogenous H(2)O(2) content and caused carbonylation of storage proteins and of several metabolic enzymes. Under the same conditions, we also monitored the expression of two MAPK genes known to be activated by H(2)O(2) in adult pea plants. The expression of one of them, PsMAPK2, largely increased upon pea seed imbibition in H(2)O(2) , whereas no change could be observed in expression of the other, PsMAPK3. The levels of several phytohormones such as 1-aminocyclopropane carboxylic acid, indole-3-acetic acid and zeatin appeared to correlate with the measured oxidative indicators and with the expression of PsMAPK2. Globally, our results suggest a key role of H(2)O(2) in the coordination of pea seed germination, acting as a priming factor that involves specific changes at the proteome, transcriptome and hormonal levels.