ABSTRACT: Developmental stage specificity of transcriptional, biochemical and CO2 efflux responses of leaf dark respiration to growth of Arabidopsis thaliana at elevated [CO2]
Project description:Plant respiration responses to elevated growth [CO2] are key uncertainties in predicting future crop and ecosystem function. In particular, the effects of elevated growth [CO2] on respiration over leaf development are poorly understood. This study tested the prediction that, due to greater whole-plant photoassimilate availability and growth, elevated [CO2] induces transcriptional reprogramming and a stimulation of nighttime respiration in leaf primordia, expanding leaves, and mature leaves of Arabidopsis thaliana. In primordia, elevated [CO2] altered transcript abundance, but not for genes encoding respiratory proteins. In expanding leaves, elevated [CO2] induced greater glucose content and transcript abundance for some respiratory genes, but did not alter respiratory CO2 efflux. In mature leaves, elevated [CO2] led to greater glucose, sucrose and starch content, plus greater transcript abundance for many components of the respiratory pathway, and greater respiratory CO2 efflux. Therefore, growth at elevated [CO2] stimulated dark respiration only after leaves transitioned from carbon sinks into carbon sources. This coincided with greater photoassimilate production by mature leaves under elevated [CO2] and peak respiratory transcriptional responses. It remains to be determined if biochemical and transcriptional responses to elevated [CO2] in primordial and expanding leaves are essential prerequisites for subsequent alterations of respiratory metabolism in mature leaves.
Project description:Plant respiration responses to elevated growth [CO2] are key uncertainties in predicting future crop and ecosystem function. In particular, the effects of elevated growth [CO2] on respiration over leaf development are poorly understood. This study tested the prediction that, due to greater whole-plant photoassimilate availability and growth, elevated [CO2] induces transcriptional reprogramming and a stimulation of nighttime respiration in leaf primordia, expanding leaves, and mature leaves of Arabidopsis thaliana. In primordia, elevated [CO2] altered transcript abundance, but not for genes encoding respiratory proteins. In expanding leaves, elevated [CO2] induced greater glucose content and transcript abundance for some respiratory genes, but did not alter respiratory CO2 efflux. In mature leaves, elevated [CO2] led to greater glucose, sucrose and starch content, plus greater transcript abundance for many components of the respiratory pathway, and greater respiratory CO2 efflux. Therefore, growth at elevated [CO2] stimulated dark respiration only after leaves transitioned from carbon sinks into carbon sources. This coincided with greater photoassimilate production by mature leaves under elevated [CO2] and peak respiratory transcriptional responses. It remains to be determined if biochemical and transcriptional responses to elevated [CO2] in primordial and expanding leaves are essential prerequisites for subsequent alterations of respiratory metabolism in mature leaves. Arabidopsis plants were grown in either ambient (370 ppm) or elevated (750 ppm) CO2. Leaf number 10 was harvested when it was a primordia, expanding, or mature in each of the CO2 treatments.
Project description:In this study we explain the physiological, biochemical and gene expression mechanisms adopted by nitrate-fed Arabidopsis thaliana plants growing under elevated [CO2], highlighting the importance of root-to-shoot interactions in these responses The transcriptomic approach (conducted at the root and shoot level) revealed that exposure to 800 ppm [CO2] conditioned the expression of genes involved in the transport of nitrate and mineral elements.
Project description:In this study we explain the physiological, biochemical and gene expression mechanisms adopted by ammonium nitrate-fed Arabidopsis thaliana plants growing under elevated [CO2], highlighting the importance of root-to-shoot interactions in these responses A transcriptomic analysis enabled the identification of photoassimilate allocation and remobilization as fundamental process used by the plants to maintain the outstanding photosynthetic performance. Moreover, based on the relationship between plant carbon status and hormone functioning, the transcriptomic analyses provided an explanation of why phenology accelerates in elevated [CO2] conditions.
Project description:In this study we explain the physiological, biochemical and gene expression mechanisms adopted by ammonium nitrate-fed Arabidopsis thaliana plants growing under elevated [CO2], highlighting the importance of root-to-shoot interactions in these responses A transcriptomic analysis enabled the identification of photoassimilate allocation and remobilization as fundamental process used by the plants to maintain the outstanding photosynthetic performance. Moreover, based on the relationship between plant carbon status and hormone functioning, the transcriptomic analyses provided an explanation of why phenology accelerates in elevated [CO2] conditions.
Project description:Elevated atmospheric CO2 can influence the structure and function of rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizosphere of soybean plants exposed to elevated atmospheric CO2. The results of microarray analyses indicated that atmospheric elevated CO2 concentration indirectly influences on expression of large number of Bradyrhizobium genes through soybean roots. In addition, genes involved in C1 metabolism, denitrification and FixK2-associated genes, including those involved in nitrogen fixation, microanaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2 in the rhizosphere, relative to plants and bacteria grown under ambient CO2 growth conditions. The expression profile of genes involved in lipochitinoligosaccharide Nod factor biosynthesis and negative transcriptional regulators of nodulation genes, nolA and nodD2, were also influenced by plant growth under conditions of elevated CO2. Taken together, results of these studies indicate that growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizosphere, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency.
Project description:Transcriptional reprogramming and stimulation of leaf respiration by elevated CO2 concentration is diminished, but not eliminated, under limiting nitrogen supply.
Project description:Elevated atmospheric CO2 can influence the structure and function of rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizosphere of soybean plants exposed to elevated atmospheric CO2. Transciptomic expression profiles indicated that genes involved in carbon/nitrogen metabolism, and FixK2-associated genes, including those involved in nitrogen fixation, microanaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2, relative to plants and bacteria grown under ambient CO2 growth conditions. The expression profile of genes involved in lipochitinoligosaccharide Nod factor biosynthesis and negative transcriptional regulators of nodulation genes, nolA and nodD2, were also influenced by plant growth under conditions of elevated CO2. Taken together, results of these studies indicate that growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizosphere, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency. Bradyrhizobium japonicum strains were grown in the soybean rhizosphere under two different CO2 concentrations. Transcriptional profiling of B. japonicum was compared between cells grown under elevated CO2 and ambient conditions. Four biological replicates of each treatment were prepared, and four microarray slides were used for each strain.
Project description:Transcriptional reprogramming and stimulation of leaf respiration by elevated CO2 concentration is diminished, but not eliminated, under limiting nitrogen supply. Arabidopsis plants were grown in either ambient (370 ppm) or elevated (750 ppm) CO2 with either ample N supply or limiting N supply. Leaf tissue was harvested from youngest most fully expanded leaves 35 days after plant germination at either midday or midnight.
