Project description:Background: The unprecedented rise in atmospheric CO2 concentration and injudicious fertilization or heterogeneous distribution of Mg in the soil warrant further research to understand the synergistic and holistic mechanisms involved in the plant growth regulation. The objective of this work is to understand responses in plants along with interactive effect of elevated CO2 and Mg levels by comparing data on single stress with that of combined stresses. Results: This study investigated the influence of elevated CO2 (800 μL L−1) on physiological and transcriptomic profiles in Arabidopsis cultured in hydroponic media treated with 1 μM (low), 1000 μM (normal) and 10000 μM (high) Mg2+. Following 7-d treatment, elevated CO2 increased the shoot growth and chlorophyll content under both low and normal Mg supply, whereas root growth was improved exclusively under normal Mg nutrition. Notably, the effect of elevated CO2 on mineral homeostasis in both shoots and roots was less than that of Mg supply. Irrespective of CO2 treatment, high Mg increased leaf number but decreased root growth and absorption of P, K, Ca, Fe and Mn whereas low Mg increased the concentration of P, K, Ca and Fe in leaves. Elevated CO2 decreased the expression of genes related to cadmium response, cell redox homeostasis and lipid localization, but enhanced photosynthesis, signal transduction, protein phosphorylation, NBS-LRR disease resistance proteins and subsequently programmed cell death in low-Mg shoots. By comparison, elevated CO2 enhanced the response of lipid localization (mainly LTP transfer protein/protease inhibitor), endomembrane system, heme binding and cell wall modification in high-Mg roots. Some of these transcriptomic results are substantially in accordance with our physiological and/or biochemical analysis. Conclusions: Contrasting changes were found between roots and shoots with the shoot transcriptome being more severely affected by low Mg while the root transcriptome more affected by high Mg. Elevated CO2 had a greater effect on transcript response in low Mg-fed shoots as well as in high Mg-fed roots. The present findings broaden our current understanding on the interactive effect of elevated CO2 and Mg levels in the Arabidopsis, which may help to design the novel metabolic engineering strategies to cope with Mg deficiency/excess in crops under elevated CO2.
Project description:In the present study, we sought genes that are involved in the variation of the enhancement of plant growth rate among the Arabidopsis thaliana ecotypes in elevated CO2 condition. We performed a combination analysis of a genome wide association study (GWAS), and a transcriptome study to seek the candidate genes. GWAS was performed using the growth analysis data obtained at Oguchi et al. and the whole genome data from 31 ecotypes. The transcriptome analysis was performed for 6 ecotypes that had contrasting CO2 responses in the growth rate. We analyzed not only annotated coding genes but also small coding genes (30–100 amino acids) identified by Hanada et al., most of which were shown to play roles in cell-to-cell signaling, because it has been shown that a number of small coding genes play significant roles in environmental responses. We also studied the effect of the altered expression of the candidate genes on the plant growth rate in elevated CO2 condition using over-expression (OX) transgenics and RNA interference (RNAi) transgenics. We show that transgenic plants of three genes had significantly higher growth rate under the elevated CO2 condition.
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: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.