title: Targeting of Cameleons to various subcellular compartments reveals a strict cytoplasmic/mitochondrial Ca²⁺ handling relationship in plant cells.
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.
authors.affiliation: Dipartimento di Biologia, Università degli Studi di Padova, Via U. Bassi 58/B, 35131 Padova, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Loro
authors.forename: Ilaria
authors.initials: I
authors.lastname: Drago
authors.forename: Tullio
authors.initials: T
authors.lastname: Pozzan
authors.forename: Fiorella Lo
authors.initials: FL
authors.lastname: Schiavo
authors.forename: Michela
authors.initials: M
authors.lastname: Zottini
authors.forename: Alex
authors.initials: A
authors.lastname: Costa
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism*; D009997:Osmotic Pressure; D018517:Plant Roots / Q000166:cytology; D054046:Plant Stomata / Q000166:cytology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D005456:Fluorescent Dyes; D008164:Luminescent Proteins; D002118:Calcium