Potential involvement of rapeseed (Brassica napus L.) metallothioneins in the hydrogen peroxide‐induced regulation of seed vigour

Germination is a crucial process in crop plant life cycle that determines future yield. Hydrogen peroxide plays a significant role in both dormancy release and seed ageing. The potential of the rapeseed metallothioneins (BnMT1‐4) as reactive oxygen species scavengers was investigated. In the presence of H₂O₂, bacterial cells expressing BnMT1‐4 had higher growth rate than control cells. However, such effect was not observed in an oxidative stress oversensitive yap‐1Δ yeast mutant strain expressing BnMT1‐4. Next, it was shown that H₂O₂, up to 100 and 10 mM, promotes rapeseed germination rate and seedling growth, respectively. Moreover, it was demonstrated that in seeds germinating in the presence of H₂O_2, the expression of seed‐specific BnMT4 decreases to a high extent in a dose‐ and time‐dependent manner. It was shown that the decline in BnMT4 mRNA level, accelerated by up to 10 mM H₂O₂ treatment, correlates positively with increased rapeseed germination and early growth, underscoring the plausible role of BnMT4 as a H₂O₂ scavenging protein that level has to be downregulated in conditions where the compound is needed. Finally, it was demonstrated that H₂O₂ could be used as a priming agent of rapeseeds.