Involvement of the plasma membrane Ca2+-ATPase in the short-term response of Arabidopsis thaliana cultured cells to oligogalacturonides

Treatment of Arabidopsis thaliana cells with oligoga-lacturonides (OG) initiates a transient production of reactive oxygen species (IROS), the concentration of which in the medium peaks after about 20 min of treatment. The analysis of OG effects on Ca2+ fluxes shows that OG influence both Ca2+ influx and Ca2+ efflux (measured as Ca-45(2+) fluxes) in a complex way. During the first 10-15 min, OG stimulate Ca2+ influx and decrease its efflux, while at successive times of treatment, OG cause an increase of Ca2+ efflux and a slight decrease of its influx. Treatment with sub-muM concentrations of eosin yellow (EY), which selectively inhibits the Ca2+-ATPase of plasma membrane (PM), completely prevents the OG-induced increase in Ca2+ efflux. EY also suppresses the transient feature of OG-induced ROS accumulation, keeping the level of ROS in the medium high. The biochemical analysis of PM purified from OG-treated cells indicates that treatment with OG for 15 to 45 min induces a significant decrease in Ca2+-ATPase activation by exogenous calmodulin (CaM), and markedly increases the amount of CaM associated with the PM. During the same time span, OG do not influence the expression of At-ACA8, the main isoform of PM Ca2+-ATPase in suspension-cultured A. thaliana cells, and of CaM genes. Overall, the reported results demonstrate that the PM Ca2+-ATPase is involved in the response of plant cells to OG and is essential in regulation of the oxidative burst.