Abstract
BackgroundMitochondria, as recently suggested, might be involved in iron sensing and signalling pathways in plant cells. For a better understanding of the role of these organelles in mediating the Fe deficiency responses in plant cells, it is crucial to provide a full overview of their modifications occurring under Fe-limited conditions. The aim of this work is to characterize the ultrastructural as well as the biochemical changes occurring in leaf mitochondria of cucumber (Cucumis sativus L.) plants grown under Fe deficiency.Methodology/ResultsMitochondrial ultrastructure was investigated by transmission electron microscopy (TEM) and electron tomography techniques, which allowed a three-dimensional (3D) reconstruction of cellular structures. These analyses reveal that mitochondria isolated from cucumber leaves appear in the cristae junction model conformation and that Fe deficiency strongly alters both the number and the volume of cristae. The ultrastructural changes observed in mitochondria isolated from Fe-deficient leaves reflect a metabolic status characterized by a respiratory chain operating at a lower rate (orthodox-like conformation) with respect to mitochondria from control leaves.ConclusionsTo our knowledge, this is the first report showing a 3D reconstruction of plant mitochondria. Furthermore, these results suggest that a detailed characterization of the link between changes in the ultrastructure and functionality of mitochondria during different nutritional conditions, can provide a successful approach to understand the role of these organelles in the plant response to Fe deficiency.
Highlights
Iron (Fe) is an essential element for key metabolic reactions in plants, including the respiratory and photosynthetic electron transport chains located in the endosymbiotic organelles [1]
The ultrastructural changes observed in mitochondria isolated from Fe-deficient leaves reflect a metabolic status characterized by a respiratory chain operating at a lower rate with respect to mitochondria from control leaves. This is the first report showing a 3D reconstruction of plant mitochondria. These results suggest that a detailed characterization of the link between changes in the ultrastructure and functionality of mitochondria during different nutritional
Fe deficiency affects several physiological parameters in cucumber leaves Ten-day old cucumber plants grown under Fe deficiency (-Fe) displayed yellowish leaves and a reduced growth when compared to control (C) plants (Fig 1A)
Summary
Iron (Fe) is an essential element for key metabolic reactions in plants, including the respiratory and photosynthetic electron transport chains located in the endosymbiotic organelles [1]. Plants initiate various metabolic changes in response to Fe deficiency aimed at increasing Fe acquisition capacity. Such metabolic changes are strictly dependent on functional alterations occurring in essential cell compartments such as the mitochondria and chloroplasts [1, 7]. Mitochondria might be involved in regulation of Fe deficiency-induced responses by a retrograde signalling pathway [1] Such organelles represent the powerhouse of the cell and are able to activate adaptation mechanisms in responses to abiotic stress ([8] and references therein). The aim of this work is to characterize the ultrastructural as well as the biochemical changes occurring in leaf mitochondria of cucumber (Cucumis sativus L.) plants grown under Fe deficiency.
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