Annexin 1 Is a Component of eATP-Induced Cytosolic Calcium Elevation in Roots.

Extracellular ATP (eATP) has long been established in animals as an important signalling molecule but this is less understood in plants. The identification of DORN1 (Does Not Respond to Nucleotides) as the first plant eATP receptor has shown that it is fundamental to the elevation of cytosolic free Ca ([Ca]) as a possible second messenger. eATP causes other downstream responses such as increase in reactive oxygen species (ROS) and nitric oxide, plus changes in gene expression. The plasma membrane Ca influx channels involved in eATP-induced [Ca] increase remain unknown at the genetic level. Annexin 1 has been found to mediate ROS-activated Ca influx in root epidermis, consistent with its operating as a transport pathway. In this study, the loss of function Annexin 1 mutant was found to have impaired [Ca] elevation in roots in response to eATP or eADP. Additionally, this annexin was implicated in modulating eATP-induced intracellular ROS accumulation in roots as well as expression of eATP-responsive genes.