MITOCHONDRIAL CONTRIBUTION TO THE ANOXIC CA2-CULTURED CELLS( SIGNAL IN MAIZE SUSPENSION)

Anoxia induces a rapid elevation of the cytosolic Ca2+ concentration ( [Ca2+](cyt)) in maize (Zea mays L.) cells, which is caused by the rele ase of the ion from intracellular stores. This anoxic Ca2+ release is important for gene activation and survival in O-2-deprived maize seedl ings and cells. In this study we examined the contribution of mitochon drial Ca2+ to the anoxic [Ca2+](cyt) elevation in maize cells. Imaging of intramitochondrial Ca2+ levels showed that a majority of mitochond ria released their Ca2+ in response to anoxia and took up Ca2+ upon re oxygenation. We also investigated whether the mitochondrial Ca2+ relea se contributed to the increase in [Ca2+](cyt) under anoxia. Analysis o f the spatial association between anoxic [Ca2+](cyt) changes and the d istribution oi mitochondrial and other intracellular Ca2+ stores revea led that the largest [Ca2+](cyt) increases occurred close to mitochond ria and away from the tonoplast. In addition, carbonylcyanide p-triflu oromethoxyphenyl hydrazone treatment depolarized mitochondria and caus ed a mild elevation of [Ca2+](cyt) under aerobic conditions but preven ted a [Ca2+](cyt) increase in response to a subsequent anoxic poise. T hese results suggest that mitochondria play an important role in the a noxic elevation of [Ca2+](cyt) and participate in the signaling of O-2 deprivation.