Subcellular investigation of photosynthesis-driven carbon assimilation in the symbiotic reef coral Pocillopora damicornis.

Reef-building corals form essential, mutualistic endosymbiotic associations with photosynthetic Symbiodinium dinoflagellates, providing their animal host partner with photosynthetically derived nutrients that allow the coral to thrive in oligotrophic waters. However, little is known about the dynamics of these nutritional interactions at the (sub)cellular level. Here, we visualize with submicrometer spatial resolution the carbon and nitrogen fluxes in the intact coral-dinoflagellate association from the reef coral Pocillopora damicornis by combining nanoscale secondary ion mass spectrometry (NanoSIMS) and transmission electron microscopy with pulse-chase isotopic labeling using [(13)C]bicarbonate and [(15)N]nitrate. This allows us to observe that (i) through light-driven photosynthesis, dinoflagellates rapidly assimilate inorganic bicarbonate and nitrate, temporarily storing carbon within lipid droplets and starch granules for remobilization in nighttime, along with carbon and nitrogen incorporation into other subcellular compartments for dinoflagellate growth and maintenance, (ii) carbon-containing photosynthates are translocated to all four coral tissue layers, where they accumulate after only 15 min in coral lipid droplets from the oral gastroderm and within 6 h in glycogen granules from the oral epiderm, and (iii) the translocation of nitrogen-containing photosynthates is delayed by 3 h. IMPORTANCE: Our results provide detailed in situ subcellular visualization of the fate of photosynthesis-derived carbon and nitrogen in the coral-dinoflagellate endosymbiosis. We directly demonstrate that lipid droplets and glycogen granules in the coral tissue are sinks for translocated carbon photosynthates by dinoflagellates and confirm their key role in the trophic interactions within the coral-dinoflagellate association

The ID23-2 structural biology microfocus beamline at the ESRF

Beamline ID23-2, the first dedicated and highly automated high-throughput monochromatic macromolecular crystallography microfocus beamline, is described

Highly dynamic cellular-level response of symbiotic coral to a sudden increase in environmental nitrogen

Metabolic interactions with endosymbiotic photosynthetic dinoflagellate Symbiodinium spp. are fundamental to reefbuilding corals (Scleractinia) thriving in nutrient-poor tropical seas. Yet, detailed understanding at the single-cell level of nutrient assimilation, translocation, and utilization within this fundamental symbiosis is lacking. Using pulse-chase 15N labeling and quantitative ion microprobe isotopic imaging (NanoSIMS; nanoscale secondary-ion mass spectrometry), we visualized these dynamic processes in tissues of the symbiotic coral Pocillopora damicornis at the subcellular level. Assimilation of ammonium, nitrate, and aspartic acid resulted in rapid incorporation of nitrogen into uric acid crystals (after ~45 min), forming temporary N storage sites within the dinoflagellate endosymbionts. Subsequent intracellular remobilization of this metabolite was accompanied by translocation of nitrogenous compounds to the coral host, starting at ~6 h. Within the coral tissue, nitrogen is utilized in specific cellular compartments in all four epithelia, including mucus chambers, Golgi bodies, and vesicles in calicoblastic cells. Our study shows how nitrogen-limited symbiotic corals take advantage of sudden changes in nitrogen availability; this opens new perspectives for functional studies of nutrient storage and remobilization in microbial symbioses in changing reef environments. IMPORTANCE The methodology applied, combining transmission electron microscopy with nanoscale secondary-ion mass spectrometry (NanoSIMS) imaging of coral tissue labeled with stable isotope tracers, allows quantification and submicrometric localization of metabolic fluxes in an intact symbiosis. This study opens the way for investigations of physiological adaptations of symbiotic systems to nutrient availability and for increasing knowledge of global nitrogen and carbon biogeochemical cycling. © 2013 Kopp et al

Results of x-ray mirror round-robin metrology measurements at the APS, ESRF, and SPring-8 optical metrology laboratories

This paper presents the first series of round-robin metrology measurements of x-ray mirrors organized at the Advanced Photon Source (APS) in the USA, the European Synchrotron Radiation Facility in France, and the Super Photon Ring (SPring-8) (in a collaboration with Osaka University,) in Japan. This work is part of the three institutions' three-way agreement to promote a direct exchange of research information and experience amongst their specialists. The purpose of the metrology round robin is to compare the performance and limitations of the instrumentation used at the optical metrology laboratories of these facilities and to set the basis for establishing guidelines and procedures to accurately perform the measurements. The optics used in the measurements were selected to reflect typical, as well as state of the art, in mirror fabrication. The first series of the round robin measurements focuses on flat and cylindrical mirrors with varying sizes and quality. Three mirrors (two flats and one cylinder) were successively measured using long trace profilers. Although the three facilities' LTPs are of different design, the measurements were found to be in excellent agreement. The maximum discrepancy of the rms slope error values is 0.1 μrad, that of the rms shape error was 3 nm, and they all relate to the measurement of the cylindrical mirror. The next round-robin measurements will deal with elliptical and spherical optics.Lahsen Assoufid, Amparo Rommeveaux, Haruhiko Ohashi, Kazuto Yamauchi, Hidekazu Mimura, Jun Qian, Olivier Hignette, Tetsuya Ishikawa, Christian Morawe, Albert Macrander, Ali Khounsary, and Shunji Goto "Results of x-ray mirror round-robin metrology measurements at the APS, ESRF, and SPring-8 optical metrology laboratories", Proc. SPIE 5921, Advances in Metrology for X-Ray and EUV Optics, 59210J (16 September 2005); https://doi.org/10.1117/12.623209.Optics and Photonics 2005, 2005, San Diego, California, United State

The toroidal mirror for single-pulse experiments on ID09B

Abstract ID09 is a dual-purpose beamline dedicated to time-resolved and high-pressure experiments. The time-resolved experiments use a high-speed chopper to isolate single pulses of x-rays. The chopper is installed near the sample (focal spot) and the shortest usable opening time depends on the sharpness of the vertical focusing. In the 16-bunch mode, the opening window of the chopper has to be reduced to 0.300 µs to select single pulses of x-rays. This can only be achieved by lowering the height in the chopper tunnel to 0.143 mm. To ensure a reasonable transmission though the tunnel, we have built a very precise toroidal mirror that focuses the beam 22.4 m downstream in M= 0.677 geometry. The 1.0-m long silicon mirror is curved by gravity into a near perfect toroid with a meridional radius of 9.9 km. The curvature is fine-tuned by a push stepper motor that works from below. The figure error from the gravity sag and the correcting force is less than 0.3 µrad and the polishing error is 0.7 µrad (rms) over the central 450-mm part of the mirror. The measured size of the polychromatic focus is 0.100 x 0.070 mmh x mmv in agreement with the prediction from the long-trace-profiler at the ESRF. The small focus, which integrates the entire central cone of the U17 undulator, is the result of superb optical quality, fine-control of curvature, a strain-free mount, a vibration free cooling system and careful alignment

X-ray transfocators: focusing devices based on compound refractive lenses

A tunable X-ray focusing and/or monochromating device, called a transfocator, is described. Examples of its implementation on ID11 at the ESRF are given

Iron Storage within Dopamine Neurovesicles Revealed by Chemical Nano-Imaging

Altered homeostasis of metal ions is suspected to play a critical role in neurodegeneration. However, the lack of analytical technique with sufficient spatial resolution prevents the investigation of metals distribution in neurons. An original experimental setup was developed to perform chemical element imaging with a 90 nm spatial resolution using synchrotron-based X-ray fluorescence. This unique spatial resolution, combined to a high brightness, enables chemical element imaging in subcellular compartments. We investigated the distribution of iron in dopamine producing neurons because iron-dopamine compounds are suspected to be formed but have yet never been observed in cells. The study shows that iron accumulates into dopamine neurovesicles. In addition, the inhibition of dopamine synthesis results in a decreased vesicular storage of iron. These results indicate a new physiological role for dopamine in iron buffering within normal dopamine producing cells. This system could be at fault in Parkinson's disease which is characterized by an increased level of iron in the substancia nigra pars compacta and an impaired storage of dopamine due to the disruption of vesicular trafficking. The re-distribution of highly reactive dopamine-iron complexes outside neurovesicles would result in an enhanced death of dopaminergic neurons

Du rôle respectif de l'alphabet, de l'image et des techniques audiovisuelles dans la diffusion de la culture

Hignette Marcel. Du rôle respectif de l'alphabet, de l'image et des techniques audiovisuelles dans la diffusion de la culture . In: Les Cahiers de la publicité, n°19, La révolution informatique. pp. 12-13