Waves of information: Simultaneous imaging of ER and cytosolic Ca2+ dynamics reveals long distance ER Ca2+ waves in plants (Plant Physiol.)

Calcium (Ca²⁺) signaling regulates a host of stress and developmental responses in plants. Apart from increases in cytosolic Ca²⁺ concentration ([Ca²⁺]_Cyt.), organellar signals play a key role in shaping the cytosolic signaling events. In an attempt to understand the Ca²⁺ dynamics in the endoplasmic reticulum (ER), Resentini and colleagues analyzed Ca²⁺ signaling simultaneously in the ER and cytosol using two intensiometric Ca²⁺ biosensors localized to the two compartments. Application of adenosine triphosphate (ATP) and naphthalene acetic acid (NAA) generated ER Ca²⁺ signals in single cells that temporally succeeded cytosolic signals with a lag of about 5 secs. Interestingly, treatment with cyclopiazonic acid (CPA), a specific inhibitor of ER Ca²⁺-ATPases, resulted in a significant dip in [Ca²⁺]_ER, with a concomitant increase in [Ca²⁺]_Cyt., implying a continuous, ER-type Ca²⁺-ATPases (ECA)-mediated transport of Ca²⁺ from the cytosol to the ER lumen. Leaf wounding in a soil-grown plant produced travelling Ca²⁺ waves in the ER that followed the well-studied cytosolic Ca²⁺ waves at both local as well as distal leaves. This work underscores the need to simultaneous measure Ca²⁺ signaling events in different subcellular compartments to better appreciate the complexities underlying cellular Ca²⁺ signaling. (Summary by Pavithran Narayanan @pavi_narayanan). Plant Physiology. 10.1093/plphys/kiab251