Role of the phosphoinositide pathway in the light-dependent C-4 phosphoenolpyruvate carboxylase phosphorylation cascade in Digitaria sanguinalis protoplasts

Stimulus-response coupling in animal cells frequently involves the hydrolys is of PtdIns(4,5)P-2 which is catalysed by phosphoinositide-specific phosph olipase C (PI-PLC). There is an increasing body of evidence for PI-PLC-base d signalling in plant cells; however, the physiological role of this system remains poorly documented in plants. Our data provide the first evidence t hat a PI-PLC-based signalling system is a committed step in the transductio n chain controlling the phosphorylation state of C-4 phosphoenolpyruvate ca rboxylase (PEPC), the regulation of which is central to the assimilation of atmospheric CO2 in C-4 plants.