Multi-layer Regulation of Rubisco in Response to Altered Carbon Status in Synechococcus elongatus PCC 7942

Photosynthetic organisms possess a variety of mechanisms to achieve balance between absorbed light (source) and the capacity to metabolically utilize or dissipate this energy (sink). While regulatory processes that detect changes in metabolic status/balance are relatively well-studied in plants, analogous pathways remain poorly characterized in photosynthetic microbes. Herein, we explore systemic changes that result from alterations in carbon availability in the model cyanobacterium Synechococcus elongatus PCC 7942 by taking advantage of an engineered strain where influx/efflux of a central carbon metabolite, sucrose, can be regulated experimentally. We observe that induction of a high-flux sucrose export pathway leads to depletion of internal carbon storage pools (glycogen), and concurrent increases in photosynthetic parameters. Further, a proteome-wide analysis and fluorescence reporter-based analysis revealed that upregulated factors following the activation of the metabolic sink are strongly concentrated on ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) and axillary modules involved in Rubisco maturation. Carboxysome number and Rubisco activity also increase following engagement of sucrose secretion. Conversely, reversing the flux of sucrose by feeding exogenous sucrose heterologously results in increased glycogen pools, decreased Rubisco abundance, decreased photosystem II quantum efficiency, and carboxysome reorganization. Our data suggest that Rubisco activity and organization are key outputs connected to regulatory pathways involved in metabolic balancing in cyanobacteria.

Terrestrial ecosystems buffer inputs through storage and recycling of elements

This study presents a conceptual framework of buffering through storage and recycling of elements in terrestrial ecosystems and reviews the current knowledge about storage and recycling of elements in plants and ecosystems. Terrestrial ecosystems, defined here as plant-soil systems, buffer inputs from the atmosphere and bedrock through storage and recycling of elements, i.e., they dampen and delay their responses to inputs. Our framework challenges conventional paradigms of ecosystem resistance derived from plant community dynamics, and instead shows that element pools and fluxes have an overriding effect on the sensitivity of ecosystems to environmental change. While storage pools allow ecosystems to buffer variability in inputs over short to intermediate periods, recycling of elements enables ecosystems to buffer inputs over longer periods. The conceptual framework presented here improves our ability to predict the responses of ecosystems to environmental change. This is urgently needed to define thresholds which must not be exceeded to guarantee ecosystem functioning. This study provides a framework for future research to explore the extent to which ecosystems buffer variability in inputs.

Chiral monoterpenes reveal forest emission mechanisms and drought responses

Monoterpenes exist in mirror image forms called enantiomers, but their individual formation pathways in plants and ecological functions are poorly understood, as enantiomers are usually measured and modelled together. Here we present enantiomerically separated atmospheric monoterpene and isoprene data from an enclosed tropical rainforest ecosystem without photo-chemistry during a four-month controlled drought and rewetting experiment. Surprisingly, the enantiomers showed distinct diel emission peaks, which responded differently to progressive drying. Isotopic labelling established that vegetation emitted (-)-α-pinene mainly de novo while (+)-α-pinene was emitted from storage pools. As drought stress increased, (-)-α-pinene emis-sions shifted to storage pools, which are released later in the day, favouring cloud formation. The α-pinene enantiomers each correlated better with other monoterpenes than with each other, indicating different enzymatic controls. These results show that enantiomeric distribution is key to understanding the processes driving monoterpene emission from ecosystems and to predict-ing atmospheric feedbacks in response to climate change.

Radiation Tolerant 3D Laser Scanner for Structural Inspections in Nuclear Reactor Vessels and Fuel Storage Pools

Accurate and timely assessment of displacements and/or structural damages in nuclear reactor vessels’ components is a key action in routine inspections for planning maintenance and repairs but also in emergency situations for mitigating consequences of nuclear incidents. Nevertheless, all these components are maintained underwater and reside in high-radiation fields thus imposing harsh operative conditions to inspection devices which must cope with effects such as Cerenkov radiation background, Total Ionizing Radiation (TID), and occlusions in the detectors’ field of view. To date, ultrasonic techniques and video cameras are in use for inspection of components’ integrity and with measurements of volumetric and surface crack opening displacements, respectively. The present work reports the realization of a radiation tolerant laser scanner and the results of tests in a nuclear research reactor vessel for acquisition of 3D models of critical components. The device, qualified for underwater operation and for withstanding up to 1 mGy of TID, is based on a 515 nm laser diode and a fast-scanning electro-optic unit. To evaluate performances in a significant but controlled environment, the device has been deployed in the vessel of a research reactor operated by ENEA in the Casaccia Research Centre in Rome (Italy). A 3D model of the fuel rods assembly through a cooling water column of 7 m has been acquired. The system includes proprietary postprocessing software that automatically recognizes components of interest and provides dimensional analysis. Possible application fields of the system stretch to dimensional analysis also in spent nuclear fuel storage pools.

Extracellular Granzyme K Modulates Angiogenesis by Regulating Soluble VEGFR1 Release From Endothelial Cells

Angiogenesis is crucial for normal development and homeostasis, but also plays a role in many diseases including cardiovascular diseases, autoimmune diseases, and cancer. Granzymes are serine proteases stored in the granules of cytotoxic cells, and have predominantly been studied for their pro-apoptotic role upon delivery in target cells. A growing body of evidence is emerging that granzymes also display extracellular functions, which largely remain unknown. In the present study, we show that extracellular granzyme K (GrK) inhibits angiogenesis and triggers endothelial cells to release soluble VEGFR1 (sVEGFR1), a decoy receptor that inhibits angiogenesis by sequestering VEGF-A. GrK does not cleave off membrane-bound VEGFR1 from the cell surface, does not release potential sVEGFR1 storage pools from endothelial cells, and does not trigger sVEGFR1 release via protease activating receptor-1 (PAR-1) activation. GrK induces de novo sVEGFR1 mRNA and protein expression and subsequent release of sVEGFR1 from endothelial cells. GrK protein is detectable in human colorectal tumor tissue and its levels positively correlate with sVEGFR1 protein levels and negatively correlate with T4 intratumoral angiogenesis and tumor size. In conclusion, extracellular GrK can inhibit angiogenesis via secretion of sVEGFR1 from endothelial cells, thereby sequestering VEGF-A and impairing VEGFR signaling. Our observation that GrK positively correlates with sVEGFR1 and negatively correlates with angiogenesis in colorectal cancer, suggest that the GrK-sVEGFR1-angiogenesis axis may be a valid target for development of novel anti-angiogenic therapies in cancer.

Alkalo-Thermophilic Microbial Diversity of the Tecozautla Geyser, México

Microbial mats have been studied in many thermal systems; the most iconic is Yellowstone. In Mexico, the information on microbial mats is scarce and therefore novel. In this research, the thermophilic microbial composition of samples from four areas of the Tecozautla geyser, Hidalgo, Mexico, was studied: sediments (GD), salt deposits (GA), and microbial mats (GB and GC). The samples were taken at the outlet of the geyser (94 °C) and in storage pools with temperatures of 61.5-65 °C. Sequencing of the 16S rRNA gene amplicons was carried out, obtaining 1,425,506 readings, and was analyzed through the Quantitative Insights Into Microbial Ecology software package version 2 (qiime2). 32 phyla were identified in the four samples being the most representative for the GA sample: Armatimonadetes, Chloroflexi, Cyanobacteria, and Thermi, with abundances of 46.35, 19.18, 3.27, and 1.82 %, respectively. For the GB sample, they were Proteobacteria, Bacteroidetes, Cyanobacteria, Spirochaetes, Thermi, and Firmicutes with abundances of 25.23, 22.04, 20.42, 12.31, 4.56, and 1.32 %, respectively. For the GC sample, abundances of 55.60, 9.85, 7.04, 7.01, and 6.15 % were observed for the phylum Chloroflexi, Armatimonadetes, Proteobacteria, Cyanobacteria, and Acidobacteria, respectively. Finally, for the GD sample, the most abundant phyla were Chloroflexi (36.10 %), Cyanobacteria (17.13 %), Armatimonadetes (15.59 %), Proteobacteria (5.45 %), and Nitrospirae with (3.21 %). The metabolic functionality of the microbial communities present in the samples was inferred using the 16S rRNA amplicons. This work represents the first report of the microbial communities present in the Tecozautla geyser.

Calcium ions trigger the exposure of phosphatidylserine on the surface of necrotic cells

Intracellular Ca2+ level is under strict regulation through calcium channels and storage pools including the endoplasmic reticulum (ER). Mutations in certain ion channel subunits, which cause mis-regulated Ca2+ influx, induce the excitotoxic necrosis of neurons. In the nematode Caenorhabditis elegans, dominant mutations in the DEG/ENaC sodium channel subunit MEC-4 induce six mechanosensory (touch) neurons to undergo excitotoxic necrosis. These necrotic neurons are subsequently engulfed and digested by neighboring hypodermal cells. We previously reported that necrotic touch neurons actively expose phosphatidylserine (PS), an “eat-me” signal, to attract engulfing cells. However, the upstream signal that triggers PS externalization remained elusive. Here we report that a robust and transient increase of cytoplasmic Ca2+ level occurs prior to the exposure of PS on necrotic touch neurons. Inhibiting the release of Ca2+ from the ER, either pharmacologically or genetically, specifically impairs PS exposure on necrotic but not apoptotic cells. On the contrary, inhibiting the reuptake of cytoplasmic Ca2+ into the ER induces ectopic necrosis and PS exposure. Remarkably, PS exposure occurs independently of other necrosis events. Furthermore, unlike in mutants of DEG/ENaC channels, in dominant mutants of deg-3 and trp-4, which encode Ca2+ channels, PS exposure on necrotic neurons does not rely on the ER Ca2+ pool. Our findings indicate that high levels of cytoplasmic Ca2+ are necessary and sufficient for PS exposure. They further reveal two Ca2+-dependent, necrosis-specific pathways that promote PS exposure, a “two-step” pathway initiated by a modest influx of Ca2+ and further boosted by the release of Ca2+ from the ER, and another, ER-independent, pathway. Moreover, we found that ANOH-1, the worm homolog of mammalian phospholipid scramblase TMEM16F, is necessary for efficient PS exposure in thapsgargin-treated worms and trp-4 mutants, like in mec-4 mutants. We propose that both the ER-mediated and ER-independent Ca2+ pathways promote PS externalization through activating ANOH-1.

Nutrition: Macronutrient metabolism

Food intake is sporadic and, in many cultures, occurs in three daily boluses. At the same time, energy expenditure is continuous and can vary to a large extent independently of the pattern of energy intake, although fixed or predictable demands (e.g. through occupation) means that in most persons food intake and energy expenditure are soon balanced. The body has developed complex systems that direct excess nutrients into storage pools; as they are needed, they also regulate the mobilization of nutrients from these pools. Carbohydrate, lipid, and protein (the latter a source of amino acids) are the three types of energy supply that are stored variably and assimilated from food each day. That we can carry on our daily lives without thinking about whether to store or mobilize fuels, and which to use, attests to the remarkable efficiency and refinement of these systems of metabolic control.