Oxygen Initiation of Respiration and Mitochondrial Biogenesis in Rice

Abstract

Rice growth under aerobic and anaerobic conditions allowed aspects of mitochondrial biogenesis to be identified as dependent on or independent of an oxygen signal. Analysis of transcripts encoding mitochondrial components found that a subset of these genes respond to oxygen (defined as aerobic), whereas others are relatively unaffected by oxygen availability. Mitochondria formed during growth in anaerobic conditions had reduced protein levels of tricarboxylic acid cycle components and cytochrome-containing complexes of the respiratory chain and repressed respiratory functionality. In general, the capacity of the general import pathway was found to be significantly lower in mitochondria isolated from tissue grown under anaerobic conditions, whereas the carrier import pathway capacity was not affected by changes in oxygen availability. Transcript levels of genes encoding components of the protein import apparatus were generally not affected by the absence of oxygen, and their protein abundance was severalfold higher in mitochondria isolated from anaerobically grown tissue. However, both transcript and protein abundances of the subunits of the mitochondrial processing peptidase, which in plants is integrated into the cytochrome bc 1 complex, were repressed under anaerobic conditions. Therefore, in this system, an increase in import capacity is correlated with an increase in the abundance of the cytochrome bc 1 complex, which is ultimately dependent on the presence of oxygen, providing a link between the respiratory chain and protein import apparatus.

Mitochondrial biogenesis as revealed by mitochondrial transcript profiles during germination and early seedling growth in wheat

“…structural and functional development of mitochondria (Leaver and Lonsdale, 1989). Mitochondrial biogenesis during germination and early seedling growth has been studied in peanut (Morohashi et al, 1981), cucumber (Hill et al, 1992), maize (Ehrenshaft and Brambl, 1990;Li et al, 1996;Logan et al, 2001) and rice (Howell et al, 2006(Howell et al, , 2007. It has been reported that poorly differentiated but fully Edited by Toru Terachi * Corresponding author.…”

Profiling of mitochondrial transcriptome in germinating wheat embryos and seedlings subjected to cold, salinity and osmotic stresses

“…Under 3-days high salinity stress even a greater increase occurred in the amount of cox2 transcript. Howell et al (2007) reported that cox2 was insensitive to oxygen until 12 h but then the level of its transcript increased by 3-fold under aerobic condition compared with anaerobic condition. Transcript level of the wheat AOX gene, Waox1a, showed a more than four-fold increase after 1-day low temperature stress as compared to the normal condition but it decreased after the 2nd day and remained unchanged until the 3rd day.…”

“…The extent of contribution of organellar gene expression in such stress response however remains largely unknown. A few studies have focused on mitochondrial gene expression, including ones in tobacco cultured cells during nutrient starvation (Giegé et al, 2005) and in rice plants germinating under low oxygen conditions (Howell et al, 2007). In rice, some mitochondrial components (cox2, cox5b-2, F 1 β-1, F 1 β-2) respond to low oxygen availability at both transcript and protein levels, while others like nad9 and cob remain unaffected (Howell et al, 2007).…”

“…A few studies have focused on mitochondrial gene expression, including ones in tobacco cultured cells during nutrient starvation (Giegé et al, 2005) and in rice plants germinating under low oxygen conditions (Howell et al, 2007). In rice, some mitochondrial components (cox2, cox5b-2, F 1 β-1, F 1 β-2) respond to low oxygen availability at both transcript and protein levels, while others like nad9 and cob remain unaffected (Howell et al, 2007). In pea leaf mitochondria, various stresses imposed differential impact on mitochondrial function and stability of key matrix enzymes, with low temperature causing more damage than drought .…”

The Mitochondrial Protein Import Component, TRANSLOCASE OF THE INNER MEMBRANE17-1, Plays a Role in Defining the Timing of Germination in Arabidopsis

“…Mitochondrial function is required for the earliest steps of germination, both for ATP production and for its central role in a variety of metabolic processes (Law et al, 2014). Detailed analysis of mitochondrial respiration during germination in rice (Oryza sativa) revealed a biphasic increase in respiration rate, whereby oxygen uptake is detectable almost immediately on imbibition, which then stabilizes for some time before increasing greater than 4-fold (Howell et al, 2007a). The latter increase in respiration is accompanied by an increase in mitochondrial cristae structure and is accompanied by a temporal change in abundance for a variety of transcripts encoding components involved in mitochondrial biogenesis, which peak prior to transcripts and proteins encoding respiratory chain components (Howell et al, 2007b;Law et al, 2012).…”