The integration of reactive oxygen species (ROS) and calcium signalling in abiotic stress responses.

Reactive oxygen species (ROS) and calcium (Ca 2+ ) signalling are interconnected in the perception and transmission of environmental signals that control plant growth, development and defence. The concept that systemically propagating Ca 2+ and ROS waves function together with electric signals in directional cell-to-cell systemic signalling and even plant-to-plant communication, is now firmly imbedded in the literature. However, relatively few mechanistic details are available regarding the management of ROS and Ca 2+ signals at the molecular level, or how synchronous and independent signalling might be achieved in different cellular compartments. This review discusses the proteins that may serve as nodes or connecting bridges between the different pathways during abiotic stress responses, highlighting the crosstalk between ROS and Ca 2+ pathways in cell signalling. We consider putative molecular switches that connect these signalling pathways and the molecular machinery that achieves the synergistic operation of ROS and Ca 2+ signals.