Cd-induced signaling pathways in plants: Possible regulation of PC synthase by protein phosphatase 1

Phyhtochelatins (PCS) are non-protein thiols synthesized through glutathione transpeptidation, due to the enzymatic activity of phytochelatin synthase, and are one of the most important metal tolerance mechanisms in plants. The present work was designed to identify the importance of plant protein phosphatase 1 in Cd signaling and PC production, by analyzing its role on GSH production and PC synthesis, as well as on Cd absorption and metal tolerance. Throughout the time-course development of PC synthesis and Cd chelation, we monitored PP1 expression and also assessed its importance for PC synthesis and Cd tolerance by using a specific PP1 inhibitor, Cantharidin.Results provided here show that PC synthase activity can be modulated by protein phosphorylation. PP1 inhibition induced a prominent increase in PC synthesis, mostly by influencing PCS activity, but had no influence on GSH synthesis. Altogether, results suggest that under Cd-free conditions, PP1 maybe responsible for maintaining PCS inactive in the cells, and that during Cd stress it gets inhibited, enhancing PCS activity. Our findings can open new possibilities for further studies on Cd tolerance regulation in plants, where regulators of protein phosphorylation can be used to specific target PCS activity and enhance Cd uptake and tolerance.

► The present work was designed to identify the importance of plant protein phosphatase PP1 in Cd signaling and PC production. ► Results provided showed that PC synthase activity can be modulated by protein phosphorilation. ► These findings can open new possibilities for further studies on Cd tolerance regulation in plants, where regulators of protein phosphorylation can be used to specific target PCS activity and enhance Cd uptake and tolerance.