LOW-TEMPERATURE PERCEPTION IN PLANTS - EFFECTS OF COLD ON PROTEIN-PHOSPHORYLATION IN CELL-FREE-EXTRACTS

Activities of prevalent protein phosphatases decreased by nearly 95% a nd those of individual protein kinases were differentially reduced at low temperature. Inhibition of phosphatase activity at temperatures be low 12 degrees C resulted in marked hyperphosphorylation of a 58-kDa p rotein (PP58). The temperature threshold for hyperphosphorylation of P P58 coincided with the known threshold for cold-induced calcium influx . Since calcium influx is triggered by several environmental stresses, we propose that the observed direct effects of cold on the phosphoryl ation of specific proteins enable cells to couple a shared calcium sig nal to a cold-specific transduction pathway. (C) 1997 Federation of Eu ropean Biochemical Societies.