Sulphate fertilization ameliorates long-term aluminum toxicity symptoms in perennial ryegrass (Lolium perenne)

Effects of the oxanion sulphate on plant aluminum (Al3+) detoxification mechanisms are not well understood. Therefore, holistic physiological and biochemical modifications induced by progressively increased doses of sulphate fertilization in the presence of long-term Al3+ stress were investigated in the aluminum sensitive perennial ryegrass (Lolium perenne L. cvJumbo). Plant growth inhibition induced by Al3+ was decreased in response to increasing doses of sulphate supply. Aluminum concentrations measured in roots of perennial ryegrass by atomic absorption spectrometry declined significantly with increasing sulphate concentrations. In parallel, we determined a rise of sulphur in shoots and roots of perennial ryegrass. Inclusion of up to 360 μM of sulphate enhanced cysteine and glutathione biosynthesis in Al3+ (1.07 μM) treated plants. This increase of thiol-containing compounds favored all modifications in the glutathione redox balance, declining lipid peroxidation, decreasing the activity of superoxide dismutase, and modifying the expression of proteins involved in the diminution of Al3+ toxicity in roots. In particular, proteome analysis by 1D-SDS-PAGE and LC-MS/MS allowed to identify up (e.g. vacuolar proton ATPase, proteosome β subunit, etc) and down (Glyoxilase I, Ascorbate peroxidase, etc.) regulated proteins induced by Al3+ toxicity symptoms in roots. Although, sulphate supply up to 480 μM caused a reduction in Al3+ toxicity symptoms, it was not as efficient as compared to 360 μM sulphate fertilization. These results suggest that sulphate fertilization ameliorates Al3+ toxicity responses in an intracellular specific manner within Lolium perenne.