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Plant J. 2012 Jul;71(1):1-13. doi: 10.1111/j.1365-313X.2012.04968.x. Epub 2012 Apr 30.

Targeting of Cameleons to various subcellular compartments reveals a strict cytoplasmic/mitochondrial Ca²⁺ handling relationship in plant cells.

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1
Dipartimento di Biologia, Università degli Studi di Padova, Via U. Bassi 58/B, 35131 Padova, Italy.

Abstract

Here we describe use of a mitochondrial targeted Cameleon to produce stably transformed Arabidopsis plants that enable analyses of mitochondrial Ca²⁺ dynamics in planta and allow monitoring of the intra-mitochondrial Ca²⁺ concentration in response to physiological or environmental stimuli. Transgenic plants co-expressing nuclear and mitochondrial targeted Cameleons were also generated and analyzed. Here we show that mitochondrial Ca²⁺ accumulation is strictly related to the intensity of the cytoplasmic Ca²⁺ increase, demonstrating a tight association between mitochondrial and cytoplasmic Ca²⁺ dynamics. However, under all experimental conditions, mitochondrial Ca²⁺ dynamics were substantially different from those monitored in the cytoplasm, demonstrating that mitochondria do not passively sense cytosolic Ca²⁺, but actively modulate the intra-mitochondrial level of the cation. In particular, our analyses show that the kinetics of Ca²⁺ release from mitochondria are much slower than in the cytoplasm and nucleus. The mechanisms and functional implications of these differences are discussed.

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