Cell wall pectin can generate superoxide

Abstract

Superoxide dismutases present in apoplast and cell wall imply the extracellular generation of superoxide whose source and effects are not fully understood. Here we show using Electron Paramagnetic Resonance spectroscopy with spin-trap DEPMPO which is able to differentiate between hydroxyl radical and superoxide, that galacturonic acid in pectin from the cell wall can produce superoxide by transforming hydroxyl radical in the presence of oxygen. This may explain the presence of superoxide and related enzymes in the apoplast and cell wall, but more important it could have a major impact on the understanding of mechanisms by which of poly- and oligogalacturonic acids (PGA and OGA) from the cell wall regulate stress response and cell growth.