Overexpression of UCP1 in tobacco induces mitochondrial biogenesis and amplifies a broad stress response

Abstract

BackgroundUncoupling protein one (UCP1) is a mitochondrial inner membrane protein capable of uncoupling the electrochemical gradient from adenosine-5′-triphosphate (ATP) synthesis, dissipating energy as heat. UCP1 plays a central role in nonshivering thermogenesis in the brown adipose tissue (BAT) of hibernating animals and small rodents. A UCP1 ortholog also occurs in plants, and aside from its role in uncoupling respiration from ATP synthesis, thereby wasting energy, it plays a beneficial role in the plant response to several abiotic stresses, possibly by decreasing the production of reactive oxygen species (ROS) and regulating cellular redox homeostasis. However, the molecular mechanisms by which UCP1 is associated with stress tolerance remain unknown.ResultsHere, we report that the overexpression of UCP1 increases mitochondrial biogenesis, increases the uncoupled respiration of isolated mitochondria, and decreases cellular ATP concentration. We observed that the overexpression of UCP1 alters mitochondrial bioenergetics and modulates mitochondrial-nuclear communication, inducing the upregulation of hundreds of nuclear- and mitochondrial-encoded mitochondrial proteins. Electron microscopy analysis showed that these metabolic changes were associated with alterations in mitochondrial number, area and morphology. Surprisingly, UCP1 overexpression also induces the upregulation of hundreds of stress-responsive genes, including some involved in the antioxidant defense system, such as superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione-S-transferase (GST). As a consequence of the increased UCP1 activity and increased expression of oxidative stress-responsive genes, the UCP1-overexpressing plants showed reduced ROS accumulation. These beneficial metabolic effects may be responsible for the better performance of UCP1-overexpressing lines in low pH, high salt, high osmolarity, low temperature, and oxidative stress conditions.ConclusionsOverexpression of UCP1 in the mitochondrial inner membrane induced increased uncoupling respiration, decreased ROS accumulation under abiotic stresses, and diminished cellular ATP content. These events may have triggered the expression of mitochondrial and stress-responsive genes in a coordinated manner. Because these metabolic alterations did not impair plant growth and development, UCP1 overexpression can potentially be used to create crops better adapted to abiotic stress conditions.

Cold sensitivity of mitochondrial ATP synthase restricts oxidative phosphorylation in Arabidopsis thaliana

“…Furthermore, it was shown by Barreto et al . () that overexpression of UCP1 in tobacco led to increased transcription and translation of mitochondrial proteins encoded by both nuclear and mitochondrial genomes, indicating that UCP1 may be involved in retrograde signalling. Interestingly, UCP1‐overexpressing lines also displayed upregulation of the antioxidant defence system, which may be responsible for the enhanced performance of mutants under a range of abiotic stresses, including chilling.…”

“…It has been proposed by a number of workers that UCPs may play a role in preventing oxidative stress during chilling (Echtay et al ., ; Armstrong et al ., ). UCP transcripts in both Arabidopsis and potato plants have been shown to be strongly induced following exposure to low temperatures (Laloi et al ., ; Maia et al ., ); UCPs are activated by O 2 · − (Echtay et al ., ; Considine et al ., ; Norman et al ., ) and are also able to simultaneously reduce the generation of mitochondrial ROS (Kowaltowski et al ., ; Barreto et al ., ). Furthermore, it was shown by Barreto et al .…”

“…It has been proposed by a number of workers that UCPs may play a role in preventing oxidative stress during chilling (Echtay et al, 2002;Armstrong et al, 2008). UCP transcripts in both Arabidopsis and potato plants have been shown to be strongly induced following exposure to low temperatures (Laloi et al, 1997;Maia et al, 1998); UCPs are activated by O 2 Á À (Echtay et al, 2002;Considine et al, 2003;Norman et al, 2004) and are also able to simultaneously reduce the generation of mitochondrial ROS (Kowaltowski et al, 1998;Barreto et al, 2014). Furthermore, it was shown by Barreto et al (2014) that overexpression of UCP1 in tobacco led to increased transcription and translation of mitochondrial proteins encoded by both nuclear and mitochondrial genomes, indicating that UCP1 may be involved in retrograde signalling.…”

Biogenesis of mitochondria in cauliflower ( Brassica oleracea var. botrytis ) curds subjected to temperature stress and recovery involves regulation of the complexome, respiratory chain activity, organellar translation and ultrastructure

“…Ultrathin sections were obtained using Reichert UltracutS and Leica EM UC6 ultramicrotomes, and post-stained for 10 min successively in 5% uranyl citrate and a saturated lead citrate solution for analysis under a transmission electron microscope (TEM) JEM 1200EXII (Jeol). Analysis of the mitochondria number, area occupied by all mitochondria or single mitochondrion in TEM micrograph field images [9] was carried out on field images representing each variant at x7500 direct magnification. Microscopic preparations were made from at least 3 cauliflower curds in 3 independent biological replicates and the representative results were shown.…”

The Roles of Mitochondrial Reactive Oxygen Species in Cellular Signaling and Stress Response in Plants

“…The role of AOX in minimizing ROS production has been extensively reviewed (Rhoads et al, 2006;Vanlerberghe, 2013). Recently, overexpression of the Arabidopsis (Arabidopsis thaliana) uncoupler protein Uncoupling protein1 in tobacco was found to reduce the rate of ROS generation, induce the antioxidant defense system, and enhance resistance to multiple abiotic stresses (Barreto et al, 2014). Superoxide spontaneously disproportionates to H 2 O 2 and O 2 , but this can be strongly accelerated by superoxide dismutase (SOD; Møller, 2001;Morgan et al, 2008).…”