Figure 2.

Putative model integrating eATP and NO-regulated signaling pathways for root hair growth in Arabidopsis. eATP putative receptor, NADPH oxidase and Ca²⁺ channel are shown in the plasma membrane (PM). Depending on the cell type and the external stimulus, eAT P would induce Ca²⁺ channel activity and increase [Ca²⁺]_cyt leading to NO accumulation and ROS production via NADPH oxidase stimulation. In addition, NO may regulate Ca²⁺ channels by feedback activation. NO may also promote the formation of cGMP messenger. In turn, actin cytoskeleton may act as a downstream effector of NO signal transduction pathway. In parallel, auxin through NO could modulate root hair growth.