Interactions between mitochondria, endoplasmic reticulum, and actin filaments. Mitochondria-bound microfilaments are depolymerized by Lat-B and are stabilized by Jas, and either change in the actin structure promotes the opening of mPTP. Because of the close apposition of mitochondria to ER, Ca2+ released from mitochondria can activate the Ca2+-induced Ca2+ release (CICR) mechanism in ER, which triggers spontaneous [Ca2+]c spikes. The disruption of actin filaments also induces an increase in Ca2+ influx at the root hair surface. The signal of Ca2+ increase in the cytoplasm triggers final Ca2+ efflux. Mito, mitochondria; ER, endoplasmic reticulum; MF, microfilaments; CW, cell wall; PM, protoplasm membrane; PTP, permeability transition pore; CA, Ca2+-ATPase, CC, Ca2+-channel.