Redox-regulation of the expression of the peroxide-detoxifying chloroplast 2-Cys peroxiredoxin in the liverwort Riccia fluitans

Abstract.

2-Cys peroxiredoxins (2-CPs) are H₂O₂- and alkyl hydroperoxide-detoxifying enzymes, and occur in animals, fungi, bacteria and higher plants. Here, the cDNA encoding a peroxiredoxin of a multicellular cryptogamic plant was first cloned from the liverwort Riccia fluitans L., and the dependence of its expression on the cellular redox state was analysed. The presence of an N-terminal targeting signal indicates that, like 2-CPs from higher plants, Riccia 2-CP is posttranslationally imported into chloroplasts. Addition of ascorbate and other reductants suppressed 2-CP gene expression and decreased 2-CP protein levels. With ascorbate, the decrease in 2-CP transcript level was fast, concentration dependent, and correlated with the amounts of ascorbate taken up by the tissue. In an approach to identify signaling components, staurosporine was proved to be a highly potent inhibitor of ascorbate-dependent repression of 2-CP-expression. The staurosporine effect indicates that a serine/threonine-kinase is involved in ascorbate-modulated redox regulation of 2-CP expression.