Figure 2.

Schematic diagram of the calcium signaling pathway following biotic attack. After an attack, resistance elicitors are released in herbivore oral secretions (OS), precipitated, and bound to receptors, causing a rapid increase in calcium cytosolic ([Ca²⁺] _cyt) content. Calcium channels and ATP-dependent Ca²⁺ pumps in the cell membrane and cell organelles (e.g., mitochondria, vacuoles, and endoplasmic reticulum) organize Ca²⁺ ions inside and outside the cell/organelles. Greater increases in Ca²⁺ ions trigger potassium (K⁺) channel activation, causing plasma membrane potential (Vm) depolarization. Different calcium receptors (e.g., CBL–CIPK, calcineurin B-like protein- CBL interacting protein kinase, CML42/CML43, calmodulin-like proteins 42/43, and CPK3/CPK13, calcium-dependent protein kinases3/13) increase to activate transcription factors, such as HSFB2A. Finally, transcriptional regulation in the nucleus induces plant herbivore defense (Modified from [5]).