Metabolic recovery of Arabidopsis thaliana roots following cessation of oxidative stress

To cope with the various environmental stresses resulting in reactive oxygen species (ROS) production plant metabolism is known to be altered specifically under different stresses. After overcoming the stress the metabolism should be reconfigured to recover basal operation however knowledge concerning how this is achieved is cursory. To investigate the metabolic recovery of roots following oxidative stress, changes in metabolite abundance and carbon flow were analysed. Arabidopsis roots were treated by menadione to elicit oxidative stress. Roots were fed with 13C labelled glucose and the redistribution of isotope was determined in order to study carbon flow. The label redistribution through many pathways such as glycolysis, the tricarboxylic acid (TCA) cycle and amino acid metabolism were reduced under oxidative stress. After menadione removal many of the stress-related changes reverted back to basal levels. Decreases in amounts of hexose phosphates, malate, 2-oxoglutarate, glutamate and aspartate were fully recovered or even increased to above the control level. However, some metabolites such as pentose phosphates and citrate did not recover but maintained their levels or even increased further. The alteration in label redistribution largely correlated with that in metabolite abundance. Glycolytic carbon flow reverted to the control level only 18 h after menadione removal although the TCA cycle and some amino acids such as aspartate and glutamate took longer to recover. Taken together, plant root metabolism was demonstrated to be able to overcome menadione-induced oxidative stress with the differential time period required by independent pathways suggestive of the involvement of pathway specific regulatory processes

Persistent left superior vena cava: Review of the literature, clinical implications, and relevance of alterations in thoracic central venous anatomy as pertaining to the general principles of central venous access device placement and venography in cancer patients

Persistent left superior vena cava (PLSVC) represents the most common congenital venous anomaly of the thoracic systemic venous return, occurring in 0.3% to 0.5% of individuals in the general population, and in up to 12% of individuals with other documented congential heart abnormalities. In this regard, there is very little in the literature that specifically addresses the potential importance of the incidental finding of PLSVC to surgeons, interventional radiologists, and other physicians actively involved in central venous access device placement in cancer patients. In the current review, we have attempted to comprehensively evaluate the available literature regarding PLSVC. Additionally, we have discussed the clinical implications and relevance of such congenital aberrancies, as well as of treatment-induced or disease-induced alterations in the anatomy of the thoracic central venous system, as they pertain to the general principles of successful placement of central venous access devices in cancer patients. Specifically regarding PLSVC, it is critical to recognize its presence during attempted central venous access device placement and to fully characterize the pattern of cardiac venous return (i.e., to the right atrium or to the left atrium) in any patient suspected of PLSVC prior to initiation of use of their central venous access device

A research challenge vision regarding management of agricultural waste in a circular bio-based economy

Agricultural waste is a huge pool of untapped biomass resources that may even represent economic and environmental burdens. They can be converted into bioenergy and bio-based products by cascading conversion processes, within circular economy, and should be considered residual resources. Major challenges are discussed from a transdisciplinary perspective, focused on Europe situation. Environmental and economic consequences of agricultural residue management chains are difficult to assess due to their complexity, seasonality and regionality. Designing multi-criteria decision support tools, applicable at an early-stage of research, is discussed. Improvement of Anaerobic Digestion (AD), one of the most mature conversion technologies, is discussed from a technological point of view and waste feedstock geographical and seasonal variations. Using agricultural residual resources for producing high-value chemicals is a considerable challenge analysed here, taking into account innovative eco-efficient and cost-effective cascading conversion processes (bio-refinery concept). Moreover, the promotion of agricultural residues-based business is discussed through industrial ecology, to promote synergy, on a local basis, between different agricultural and industrial value chains. Finally, to facilitate a holistic approach and optimise materials and knowledge flows management, the connection of stakeholders is discussed to promote cross-sectorial collaboration and resource exchange at appropriate geographic scale

Accumulation of small heat shock proteins, including mitochondrial HSP22, induced by oxidative stress and adaptive response in tomato cells

International audienceChanges in gene expression, by application of H$_2$O$_2$, O$_2$°$^-$ generating agents (methyl viologen, digitonin) and gamma irradiation to tomato suspension cultures, were investigated and compared to the well-described heat shock response. Two-dimensional gel protein mapping analyses gave the first indication that at least small heat shock proteins (smHSP) accumulated in response to application of H$_2$O$_2$ and gamma irradiation, but not to O$_2$°$^-$ generating agents. While some proteins seemed to be induced specifically by each treatment, only part of the heat shock response was observed. On the basis of Northern hybridization experiments performed with four heterologous cDNA, corresponding to classes I-IV of pea smHSP, it could be concluded that significant amounts of class I and II smHSP mRNA are induced by H$_2$O$_2$ and by irradiation. Taken together, these results demonstrate that in plants some HSP genes are inducible by oxidative stresses, as in micro-organisms and other eukaryotic cells. HSP22, the main stress protein that accumulates following H$_2$O$_2$ action or gamma irradiation, was also purified. Sequence homology of amino terminal and internal sequences, and immunoreactivity with Chenopodium rubrum mitochondrial smHSP antibody, indicated that the protein belongs to the recently discovered class of plant mitochondrial smHSP. Heat shock or a mild H$_2$O$_2$ pretreatment was also shown to lead to plant cell protection against oxidative injury. Therefore, the synthesis of these stress proteins can be considered as an adaptive mechanism in which mitochondrial protection could be essential

Intracellular Acetyl Unit Transport in Fungal Carbon Metabolism ▿

Acetyl coenzyme A (acetyl-CoA) is a central metabolite in carbon and energy metabolism. Because of its amphiphilic nature and bulkiness, acetyl-CoA cannot readily traverse biological membranes. In fungi, two systems for acetyl unit transport have been identified: a shuttle dependent on the carrier carnitine and a (peroxisomal) citrate synthase-dependent pathway. In the carnitine-dependent pathway, carnitine acetyltransferases exchange the CoA group of acetyl-CoA for carnitine, thereby forming acetyl-carnitine, which can be transported between subcellular compartments. Citrate synthase catalyzes the condensation of oxaloacetate and acetyl-CoA to form citrate that can be transported over the membrane. Since essential metabolic pathways such as fatty acid β-oxidation, the tricarboxylic acid (TCA) cycle, and the glyoxylate cycle are physically separated into different organelles, shuttling of acetyl units is essential for growth of fungal species on various carbon sources such as fatty acids, ethanol, acetate, or citrate. In this review we summarize the current knowledge on the different systems of acetyl transport that are operational during alternative carbon metabolism, with special focus on two fungal species: Saccharomyces cerevisiae and Candida albicans

Selective induction and subcellular distribution of ACONITASE 3 reveal the importance of cytosolic citrate metabolism during lipid mobilization in <em>Arabidopsis</em>

Arabidopsis thaliana has three genes that encode distinct aconitases (ACO), but little is known about the function of each isoenzyme during plant development. In newly emerged seedlings of Arabidopsis, transcript and protein levels for ACO3 were selectively induced to yield more than 80% of total aconitase activity. Characterization of knockout mutants for each of the three ACOs suggests a major role for only ACO3 in citrate metabolism. The aco3 mutant showed delayed early seedling growth, altered assimilation of [C-14]acetate feeding and elevated citrate levels, which were nearly 4-fold greater than in wild-type, aco1 or aco2. However, both ACO1 and ACO2 are active in seedlings as shown by inhibition of aco3 growth by the toxin monofluoroacetate, and altered [C-14]acetate assimilation and metabolite levels in aco1 and aco2. Relative levels of fumarate and malate differed between aco2 and aco3, indicating metabolically isolated pools of these metabolites in seedlings. Our inability to enrich ACO protein through mitochondria isolation, and the reduced cytosolic ACO activity of the iron sulfur centre assembly mutant atm3-1, indicated a cytosolic localization of ACO3 in 3-day-old seedlings. Subsequently, we determined that more than 90% of ACO3 was cytosolic. We conclude that ACO3 is cytosolic in young seedlings and functions in citrate catabolism consistent with the operation of the classic glyoxylate and not direct catabolism of citrate within mitochondria