International audience

Introduction: Recently copy number variation (CNV) of DNA sequences has been identified throughout the human genome (Redon et al. Nature 2006). Furthermore, CNV of the CCL3L1 gene has been associated with susceptibility to HIV infection (Gonzales et al. Science 2006). CCL3L1 is a potent HIV-suppressive chemokine and ligand for the HIV coreceptor CCR5. The frequency of the HIV-protective CCR5-Δ32 deletion has been reported to be increased in hepatitis C virus (HCV) infected patients. Hence, we hypothesized that variation in the gene dose of CCL3L1 may contribute to differences in the inflammatory response to HCV. Thus, our aims were (1) to compare CNV of the CCL3L1 gene between patients with HCV infection, HCV/HIV and controls and (2) to test for association with grades of inflammation and stages of fibrosis in HCV patients.

The composition of the protein corona formed on poly(ethylene glycol)-functionalized (PEGylated) poly(glycidyl methacrylate) (PGMA) nanoparticles (NPs) was qualitatively and quantitatively compared to the protein corona on non-PEGylated PGMA NPs. Despite the reputation of PEGylated NPs for stealth functionality, we demonstrate the preferential enrichment of specific serum proteins of varied biological function in the protein corona on PEGylated NPs when compared to non-PEGylated NPs. Additionally, we suggest that the base material of polymeric NPs plays a role in the preferential enrichment of select serum proteins to the hard corona.

Einleitung: Chemokine spielen eine wichtige Rolle bei der Rekrutierung von Entzündungszellen in die Leber. Das Chemokin CCL5 (RANTES) hat eine besondere Bedeutung bei chronischen Lebererkrankungen, da es zusätzlich direkt zu einer Sternzellaktivierung führt. Kürzlich konnte gezeigt werden, dass CCL5 eine heterophile Interaktion mit CXCL4 (PF4) bildet, wodurch es zu einer Verstärkung der Wirkung von CCL5 an Zielzellen kommt. Ziel des aktuellen Projekts war daher die Charakterisierung der Bedeutung von CCL5 und CXCL4 bei Patienten mit chronischen Lebererkrankungen.

Uncoupling proteins (UCPs) occur in the inner mitochondrial membrane and dissipate the proton gradient across this membrane that is normally used for ATP synthesis. Although the catalytic function and regulation of plant UCPs have been described, the physiological purpose of UCP in plants has not been established. Here, biochemical and physiological analyses of an insertional knockout of one of the Arabidopsis UCP genes (AtUCP1) are presented that resolve this issue. Absence of UCP1 results in localized oxidative stress but does not impair the ability of the plant to withstand a wide range of abiotic stresses. However, absence of UCP1 results in a photosynthetic phenotype. Specifically there is a restriction in photorespiration with a decrease in the rate of oxidation of photorespiratory glycine in the mitochondrion. This change leads to an associated reduced photosynthetic carbon assimilation rate. Collectively, these results suggest that the main physiological role of UCP1 in Arabidopsis leaves is related to maintaining the redox poise of the mitochondrial electron transport chain to facilitate photosynthetic metabolism.

Summary Leaf respiration in the dark ( R dark ) is often measured at a single time during the day, with hot‐acclimation lowering R dark at a common measuring temperature. However, it is unclear whether the diel cycle influences the extent of thermal acclimation of R dark , or how temperature and time of day interact to influence respiratory metabolites. To examine these issues, we grew rice under 25°C : 20°C, 30°C : 25°C and 40°C : 35°C day : night cycles, measuring R dark and changes in metabolites at five time points spanning a single 24‐h period. R dark differed among the treatments and with time of day. However, there was no significant interaction between time and growth temperature, indicating that the diel cycle does not alter thermal acclimation of R dark . Amino acids were highly responsive to the diel cycle and growth temperature, and many were negatively correlated with carbohydrates and with organic acids of the tricarboxylic acid (TCA) cycle. Organic TCA intermediates were significantly altered by the diel cycle irrespective of growth temperature, which we attributed to light‐dependent regulatory control of TCA enzyme activities. Collectively, our study shows that environmental disruption of the balance between respiratory substrate supply and demand is corrected for by shifts in TCA‐dependent metabolites.

The SOL Genomics Network (SGN; http://sgn.cornell.edu) is a rapidly evolving comparative resource for the plants of the Solanaceae family, which includes important crop and model plants such as potato (Solanum tuberosum), eggplant (Solanum melongena), pepper (Capsicum annuum), and tomato (Solanum lycopersicum). The aim of SGN is to relate these species to one another using a comparative genomics approach and to tie them to the other dicots through the fully sequenced genome of Arabidopsis (Arabidopsis thaliana). SGN currently houses map and marker data for Solanaceae species, a large expressed sequence tag collection with computationally derived unigene sets, an extensive database of phenotypic information for a mutagenized tomato population, and associated tools such as real-time quantitative trait loci. Recently, the International Solanaceae Project (SOL) was formed as an umbrella organization for Solanaceae research in over 30 countries to address important questions in plant biology. The first cornerstone of the SOL project is the sequencing of the entire euchromatic portion of the tomato genome. SGN is collaborating with other bioinformatics centers in building the bioinformatics infrastructure for the tomato sequencing project and implementing the bioinformatics strategy of the larger SOL project. The overarching goal of SGN is to make information available in an intuitive comparative format, thereby facilitating a systems approach to investigations into the basis of adaptation and phenotypic diversity in the Solanaceae family, other species in the Asterid clade such as coffee (Coffea arabica), Rubiaciae, and beyond.

Salinity is responsible for large yield losses of crops around the world. Wheat is a staple food crop, and its early growth is particularly salt sensitive. Salinity stress causes adverse effects on plant growth and development at both physiological and biochemical levels. To date, numerous studies have focused on plant metabolic responses to salinity in above ground tissues, however surprisingly little is known about the metabolic responses of wheat roots exposed to salt. Within the plant, roots are most vulnerable to salinity as they are directly exposed to salt in the soil. Previous research identified the key role that Gamma Aminobutyric Acid (GABA) metabolism plays in the salt responses of shoots. This project will investigate the regulation of GABA metabolism in salt stressed roots as well as the impact of salt stress on root physiology and respiration. We exposed Scepter wheat variety to 150mM NaCl for 3 days and 6 days through gradual increment of salt and assessed biomass, chlorophyll content, Na+ and K+ levels using flame photometry, and root respiration by Q2 oxygen sensor. Scepter showed significant reduction in fresh weight and dry weight at the whole plant level and organ level after 3 days of treatment with 150 mM NaCl, salt treatment caused a reduction in relative growth rate, chlorophyll content and an increase in root to shoot ratio in salt treated plants compared to the controls. A significant increase of Na+ content was observed in both roots and shoots after 3 days and 6 days of 150 mM NaCl treatment, but K+ levels significantly declined after 3 days of salt treatment in both roots and shoots. The Na+/K+ ratio significantly increased in both shoots and roots after 3 days and 6 days of salt treatment, but roots have higher Na+/K+ ratio compared to shoots. Experiments on oxygen consumption of roots with externally added GABA showed that capacity of roots to use GABA under salt stress to drive respiration increases with salt exposure. The results highlight the implication of salt stress on plants at physiological level and suggest a possible role of GABA in root responses to salinity, further this project will use high throughput mass spectrometry based metabolomics and proteomic approaches to elucidate the metabolic and proteomic changes in roots of wheat varieties which differ in salt tolerance based on the shoot characteristics under salinity.

The primary function of mitochondria is respiration, where the catabolism of substrates is coupled to ATP synthesis via oxidative phosphorylation. In plants, mitochondrial composition is relatively complex and flexible and has specific pathways to support photosynthetic processes in illuminated leaves. Plant mitochondria also play important roles in a variety of cellular processes associated with carbon, nitrogen, phosphorus, and sulfur metabolism. Research on plant mitochondria has rapidly developed in the last few decades with the availability of the genome sequences for a wide range of model and crop plants. Recent prominent themes in plant mitochondrial research include linking mitochondrial composition to environmental stress responses, and how this oxidative stress impacts on the plant mitochondrial function. Similarly, interest in the signaling capacity of mitochondria, the role of reactive oxygen species, and retrograde and anterograde signaling has revealed the transcriptional changes of stress responsive genes as a framework to define specific signals emanating to and from the mitochondrion. There has also been considerable interest in the unique RNA metabolic processes in plant mitochondria, including RNA transcription, RNA editing, the splicing of group I and group II introns, and RNA degradation and translation. Despite their identification more than 100 years ago, plant mitochondria remain a significant area of research in the plant sciences. This Special Issue, “Plant Mitochondria”, will cover a selection of recent research topics and timely review articles in the field of plant mitochondrial research.