Glutathione plays a role in protecting leaves of Salvinia minima from Pb2+ damage associated with changes in the expression of SmGS genes and increased activity of GS

The relationship between accumulation of Pb2+ and changes in GSH biosynthesis was analyzed in both leaves and roots of the Pb2+-hyperaccumulator aquatic fern Salvinia minima, after exposure to 40 μM Pb(NO3)2. Lead accumulation in both tissues increased the accumulation of GSH, increased the enzymatic activity of glutathione synthase (GS), and caused changes in the expression levels of SmGS genes in both tissues. The damage caused by Pb on plant performance, was evaluated by the changes in the content of pigments, particularly on the carotenoids content. Lead accumulation caused more damage in roots than in leaves as indicated by the decrease on their carotenoids content. It is interesting that in leaves, the concentration of GSH, the activity of GS and the expression levels of SmGS gene were all higher than in roots. These results, together with our previous finding that roots accumulated more phytochelatins than did leaves of S. minima plants exposed to similar concentrations of lead ( Estrella et al., 2009), suggest that the Pb-hyperaccumulator aquatic fern, S. minima, displays a coordinated and differential response to Pb2+ at leaves and roots, where GSH may play an important role in protecting leaves from the detrimental effects of lead, perhaps by counteracting the effect of free radicals.

► The role of glutathione (GSH) in response to lead (heavy metal) was examined in the lead-hyperaccumulator aquatic fern S. minima. ► Lead caused more damage in roots than in leaves. ► Contrary to roots, in leaves, lead induced the expression of the SmGS gene after 1 h exposure, leaves also showed higher GS activity and higher GSH content than roots. ► It is thus suggested that GSH may play a more important role in leaves than in roots, protecting them from lead damage.