Arabidopsis thaliana CYCLIC NUCLEOTIDE‐GATED CHANNEL2 mediates extracellular ATP signal transduction in root epidermis
Abstract
Damage can be signalled by extracellular ATP (eATP) using plasma membrane (PM) receptors to effect cytosolic free Ca 2+ ([Ca 2+ ] cyt) increase as a second messenger. The downstream PM Ca 2+ channels remain enigmatic. Here, the Arabidopsis thaliana Ca 2+ channel subunit Cyclic Nucleotide-Gated Channel2 (CNGC2) was identified as a critical component linking eATP receptors to downstream [Ca 2+ ] cyt signalling in roots. eATP-induced changes in single epidermal cell PM voltage and conductance were measured electrophysiologically, changes in root [Ca 2+ ] cyt were measured with aequorin and root transcriptional changes were determined by qRT-PCR. Two cngc2 loss of function mutants were used: cngc2-3 and dnd1 (which expresses cytosolic aequorin). eATP-induced transient depolarisation of Arabidopsis root elongation zone epidermal PM voltage was Ca 2+-dependent, requiring CNGC2 but not CNGC4 (its channel co-subunit in immunity signalling). Activation of PM Ca 2+ influx currents also required CNGC2. The eATP-induced [Ca 2+ ] cyt increase and transcriptional response in cngc2 roots were significantly impaired. CNGC2 is required for eATP-induced epidermal Ca 2+ influx, causing depolarisation leading to [Ca 2+ ] cyt increase and damage-related transcriptional response.
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