Project description:Cyanidioschyzon merolae (C. merolae) is an acidophilic red alga growing in a naturally low carbon dioxide (CO2) environment. Although it uses a ribulose 1,5-bisphosphate carboxylase/oxygenase with high affinity for CO2, the survival of C. merolae relies on functional photorespiratory metabolism. In this study, we quantified the transcriptomic response of C. merolae to changes in CO2 conditions. We found distinct changes upon shifts between CO2 conditions, such as a concerted up-regulation of photorespiratory genes and responses to carbon starvation. We used the transcriptome data set to explore a hypothetical CO2 concentrating mechanism in C. merolae, based on the assumption that photorespiratory genes and possible candidate genes involved in a CO2 concentrating mechanism are co-expressed. A putative bicarbonate transport protein and two α-carbonic anhydrases were identified, which showed enhanced transcript levels under reduced CO2 conditions. Genes encoding enzymes of a PEP-CK-type C4 pathway were co-regulated with the photorespiratory gene cluster. We propose a model of a hypothetical low CO2 compensation mechanism in C. merolae integrating these low CO2-inducible components.
Project description:Six weeks old Arabidopsis plants were transferred to a low CO2 (100 ppm) environment during 24 hours and compared to control plants kept under ambient CO2 conditions. Limited CO2 availability will cause higher rates of photorespiration and affect the plant redox homeostasis. We studied the transcriptomic impact of exposing plants to a lower CO2 environment to further eliculidate the signaling pathways during photorespiratory stress.
Project description:Six weeks old Arabidopsis plants were transferred to a low CO2 (100 ppm) environment during 24 hours and compared to control plants kept under ambient CO2 conditions. Limited CO2 availability will cause higher rates of photorespiration and affect the plant redox homeostasis. We studied the transcriptomic impact of exposing plants to a lower CO2 environment to further eliculidate the signaling pathways during photorespiratory stress. After 6 weeks plants were transferred to low CO2 conditions (100 ppm) during 24 h or kept at 400 ppm CO2 (control condition). Design: 3 replicates x 2 conditions (low CO2 - ambient CO2)
Project description:The photorespiratory pathway, short photorespiration, is an essential process in oxygenic photosynthetic organisms but also reduces the efficiency of photosynthetic carbon assimilation and is hence frequently considered as a wasteful process. By comparing the response of wild-type plants and mutants impaired in photorespiration to a shift in ambient CO2 concentrations, we demonstrate that photorespiration also plays a beneficial role during short-term acclimation to reduced CO2 availability. Wild-type plants responded with few differentially expressed genes, mostly involved in drought stress, which is likely a consequence of enhanced opening of stomata and concomitant water loss upon shift toward low CO2. In contrast, mutants with impaired activity of photorespiratory enzymes were highly stressed and not able to adjust stomatal conductance to reduced external CO2 availability. The mutants´ transcriptional response was congruent, indicating a general reprogramming to deal with the consequences of reduced CO2 availability, signaled by enhanced oxygenation of ribulose-1,5 bisphosphate and amplified by the artificially impaired photorespiratory metabolism. Central in this reprogramming was the pronounced reallocation of resources from growth processes to stress responses. In conclusion, we demonstrate that unrestricted photorespiratory metabolism is a prerequisite for rapid physiological acclimation to a reduction in CO2 availability.
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:Hydrogen sulfide is an important signaling molecule in plants that regulates essential biological processes through protein persulfidation. Although numerous persulfidated proteins were found to be involved in photorespiration, little was known about sulfide-mediated regulation of photorespiration. Label-free quantitative proteomic analysis has revealed a high impact on the protein persulfidation level when plants grown under non-photorespiratory conditions are transferred to air, with the 97 % of total identified proteins more persulfidated under suppressed photorespiration. A detailed study of the effect of sulfide on important aspects associated with photorespiratory growth conditions has provided insight into the role of sulfide in protecting plants grown under suppressed photorespiration. In these conditions, sulfide amends the metabolic imbalance of carbon/nitrogen and restores ATP levels to concentrations similar to those in air grown conditions. Sulfide also plays an essential role in balancing the significant high level of ROS measured in plants under non-photorespiratory conditions to reach a similar cellular redox state in air-grown plants, through the regulation of antioxidative defenses. Furthermore, sulfide regulates another important characteristic resulting from suppression of photorespiration, such as the stomata closure, to decrease the high guard cell ROS levels and inducing the stomata aperture. In this way, sulfide signals the movement of the CO2-dependent stomata to achieve a scenario similar to that of plants growing under normal air conditions, in the opposite direction of the already established ABA-dependent movement of the stomata. Therefore, our findings suggest that the high persulfidation level under suppressed photorespiration reveals an essential role of sulfide signaling under these conditions, and with respect to stomatal movement, the outcome of this signaling is dependent on the growth/stress condition under study.