Both Ca2+ signal and microfilament(MF)dynamics play important roles in plant stress signaling.Disruption of MFs triggers cytosolic Ca2+ concentration([Ca2+]cyt)increase.However it remains to uncover the basis of how this precise regulation is achieved.In this study,through genetic screening Arabidopsis mutants that were defect in stress induced [Ca2+]cyt increase,we identified Actin Relate Protein2(Arp2)that regulated [Ca2+]cyt increase in response to salt stress.Plant lacking Arp2 or other proteins in Arp2/3 complex exhibited enhanced mitochondria-dependent NaCl-induced [Ca2+]cyt increase and hypersensitivity to salt treatments,which associated with their impaired mitochondrial activity.Furthermore,blocking enhanced mitochondrial permeability transition pore(mPTP)open or [Ca2+]cyt increase partially rescued arp2 mutant salt sensitive phenotype.Our results suggest that Arp2/3 complex regulates mitochondria-dependent calcium signal in response to salt stress.