Disruption of actin filaments induces mitochondrial Ca2+release to the cytoplasm and [Ca2+]cchanges in Arabidopsis root hairs

Abstract

Background: Mitochondria are dynamic organelles that move along actin filaments, and serve as calcium stores in plant cells. The positioning and dynamics of mitochondria depend on membrane-cytoskeleton interactions, but it is not clear whether microfilament cytoskeleton has a direct effect on mitochondrial function and Ca2+storage. Therefore, we designed a series of experiments to clarify the effects of actin filaments on mitochondrial Ca2+storage, cytoplasmic Ca2+concentration ([Ca2+]c), and the interaction between mitochondrial Ca2+and cytoplasmic Ca2+in Arabidopsis root hairs.Results: In this study, we found that treatments with latrunculin B (Lat-B) and jasplakinolide (Jas), which depolymerize and polymerize actin filaments respectively, decreased membrane potential and Ca2+stores in the mitochondria of Arabidopsis root hairs. Simultaneously, these treatments induced an instantaneous increase of cytoplasmic Ca2+, followed by a continuous decrease. All of these effects were inhibited by pretreatment with cyclosporin A (Cs A), a representative blocker of the mitochondrial permeability transition pore (mPTP). Moreover, we found there was a Ca2+concentration gradient in mitochondria from the tip to the base of the root hair, and this gradient could be disrupted by actin-acting drugs.Conclusions: Based on these results, we concluded that the disruption of actin filaments caused by Lat-B or Jas promoted irreversible opening of the mPTP, resulting in mitochondrial Ca2+release into the cytoplasm, and consequent changes in [Ca2+]c. We suggest that normal polymerization and depolymerization of actin filaments are essential for mitochondrial Ca2+storage in root hairs. © 2010 Wang et al; licensee BioMed Central Ltd.