Marennine, a blue pigment produced by the blue diatom Haslea ostrearia, is known to have some biological activities. This pigment is responsible for the greening of oysters on the West Coast of ...France. Other new species of blue diatom, H. karadagensis, H. silbo sp. inedit., H. provincialis sp. inedit, and H. nusantara, also produce marennine-like pigments with similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms present a commercial potential for the aquaculture, food, cosmetics, and health industries. Unfortunately, for a hundred years, the exact molecular structure of this bioactive compound has remained a mystery. A lot of hypotheses regarding the chemical structure of marennine have been proposed. The recent discovery of this structure revealed that it is a macromolecule, mainly carbohydrates, with a complex composition. In this study, some glycoside hydrolases were used to digest marennine, and the products were further analyzed using nuclear magnetic resonance (NMR) and mass spectroscopy (MS). The reducing sugar assay showed that marennine was hydrolyzed only by endo-1,3-β-glucanase. Further insight into the structure of marennine was provided by the spectrum of sup.1H NMR, MS, a colorimetric assay, and a computational study, which suggest that the chemical structure of marennine contains 1,3-β-glucan.
As typical transition metal dichalcogenides (TMDC), tungsten selenide (WSesub.2) nanosheets (nano-WSesub.2) are widely used in various fields due to their layered structures and highly tunable ...electronic and magnetic properties, which results in the unwanted release of tungsten (W) and selenium (Se) into the environment. However, the environmental effects of nano-WSesub.2 in plants are still unclear. Herein, we evaluated the impacts and fate of nano-WSesub.2 and micro-WSesub.2 in rice plants (Oryza sativa L.). It was found that both nano-WSesub.2 and micro-WSesub.2 did not affect the germination of rice seeds up to 5000 mg/L but nano-WSesub.2 affected the growth of rice seedlings with shortened root lengths. The uptake and transportation of WSesub.2 was found to be size-dependent. Moreover, W in WSesub.2 was oxidized to tungstate while Se was transformed to selenocysteine, selenomethionine, Sesup.IV and Sesup.VI in the roots of rice when exposed to nano-WSesub.2, suggesting the transformation of nano-WSesub.2 in rice plants. The exposure to nano-WSesub.2 brought lipid peroxidative damage to rice seedlings. However, Se in nano-WSesub.2 did not contribute to the synthesis of glutathione peroxidase (GSH-Px) since the latter did not change when exposed to nano-WSesub.2. This is the first report on the impacts and fate of nano-WSesub.2 in rice plants, which has raised environmental safety concerns about the wide application of TMDCs, such as WSesub.2 nanosheets.
Constant mesophyll conductance (g.sub.m), and two-resistance g.sub.m model (involved in resistances of cell wall and chloroplast), where g.sub.m reaches maximum under higher CO.sub.2 concentrations, ...cannot describe the phenomenon that g.sub.m decreases with increasing intercellular CO.sub.2 concentration (C.sub.i) under relatively higher CO.sub.2 concentrations. Yin et al. (2020) proposed a g.sub.m model, according to which the ratio of chloroplastic CO.sub.2 concentration (C.sub.c) to C.sub.i is constant in the two-resistance g.sub.m model, which can describe the decreasing g.sub.m with increasing C.sub.i. In the present study, we investigated the relationship between C.sub.c and C.sub.i in leaves of Japanese white birch by using simultaneous measurements of gas exchange and chlorophyll fluorescence under various CO.sub.2 concentrations, light intensities, and during progressive drought. Across the range of ambient CO.sub.2 from 50 to 1000 mumol mol.sup.-1, and light intensities of 50 to 2000 mumol m.sup.-2 s.sup.-1, measured under well irrigation, the ratio of C.sub.c to C.sub.i kept constant. During the progressive drought, overestimated C.sub.i due to stomatal patchiness and/or cuticular transpiration was empirically corrected (threshold: stomatal conductance < 0.08 mol H.sub.2O m.sup.-2 s.sup.-1) from the A/C.sub.i response measured under adequate irrigation. The ratio of C.sub.c to C.sub.i during progressive drought (predawn leaf potential reached almost equal to - 2 MPa) also remained constant irrespective of soil drying rate in various pot sizes. The present study suggests the involvement of some physiologically regulative mechanisms to keep C.sub.c:C.sub.i ratio constant, which might act on g.sub.m in addition to the physical interaction of diffusive resistances in the cell components.
During the austral winter of 2017, a bloom of Prorocentrum spp. occurred, reaching a cell density of 2.73 × 10sup.6 cells Lsup.−1, in Paracas Bay, Peru. In order to identify which, type of species ...generated this event and determine its toxicity, the values of the environmental parameters (temperature, winds and salinity) that induced the rapid growth of the dinoflagellate in this bloom were identified. A clonal culture was established for taxonomic (SEM), phylogenetic (ITS) and toxicological analysis via LC-MS/MS to determine the presence of tetrodotoxin (TTX) and whether the species represents a food safety hazard. This event coincided with the coastal upwelling process, which generated high concentrations of phytoplankton biomass (>10 mg msup.−3 chlorophyll-a) and allowed the rapid growth of P.cordatum (IMP-BG 450) in Paracas Bay. However, toxicological analyses of the IMP-BG 450 strain culture did not show the presence of TTX quantifiable through the technique used. Due to the antecedents of the presence of TTX in mollusks from other latitudes during blooms of this species, it is recommended that analyses of this toxin be carried out both in filter-feeding mollusks and in this species during a new bloom.
This work represents a modification of the Context Conditional Generative Adversarial Network as a novel implementation of a non-linear gap reconstruction approach of missing satellite-derived ...chlorophyll a concentration data. By adjusting the loss functions of the network to focus on the structural credibility of the reconstruction, high numerical and structural reconstruction accuracies have been achieved in comparison to the original network architecture. The network also draws information from proxy data, sea surface temperature, and bathymetry, in this case, to improve the reconstruction quality. The implementation of this novel concept has been tested on the Adriatic Sea. The most accurate model reports an average error of 0.06 mg msup.−3 and a relative error of 3.87%. A non-deterministic method for the gap-free training dataset creation is also devised, further expanding the possibility of combining other various oceanographic data to possibly improve the reconstruction efforts. This method, the first of its kind, has satisfied the accuracy requirements set by scientific communities and standards, thus proving its validity in the initial stages of conceptual utilisation.
The VAHINE mesocosm experiment was designed to trigger a diazotroph bloom and to follow the subsequent transfer of diazotroph derived nitrogen (DDN) in the rest of the foodweb. Three mesocosms (50 ...m.sup.3) located inside the Nouméa lagoon (New Caledonia, South West Pacific) were enriched with dissolved inorganic phosphate (DIP) in order to promote N.sub.2 fixation in these Low Nutrient Low Chlorophyll (LNLC) waters. Initial diazotrophic community were dominated by diatom diazotroph associations (DDAs), mainly by Rhizosolenia/Richelia intracellularis, and by Trichodesmium which fueled enough DDN to sustain the growth of other diverse diatom species and Synechococcus populations, that were well adapted to limiting DIP levels. After DIP fertilization (1 mM) on day 4, an initial lag time of 10 days was necessary for the mesocosm ecosystems to start building up biomass. Yet changes in community structure were already observed during this first period, with a significant drop of both Synechococcus and diatom populations, while Prochlorococcus benefited from DIP-addition. At the end of this first period, corresponding to when most added DIP was consumed, the diazotroph community changed drastically and became dominated by UCYN-C populations, which were accompanied by a monospecific bloom of the diatom Cylindrotheca closterium. During the second period, biomass increased sharply together with primary production and N.sub.2 fixation fluxes near tripled. Diatom populations, as well as Synechococcus and nano-phytoeukaryotes showed a re-increase towards the end of the experiment, showing efficient transfer of DDN to non diazotrophic phytoplankton.
Chlorophylls (Chl) play pivotal roles in energy capture, transfer and charge separation in photosynthesis. Among Chls functioning in oxygenic photosynthesis, Chl f is the most red-shifted type first ...found in a cyanobacterium Halomicronema hongdechloris. The location and function of Chl f in photosystems are not clear. Here we analyzed the high-resolution structures of photosystem I (PSI) core from H. hongdechloris grown under white or far-red light by cryo-electron microscopy. The structure showed that, far-red PSI binds 83 Chl a and 7 Chl f, and Chl f are associated at the periphery of PSI but not in the electron transfer chain. The appearance of Chl f is well correlated with the expression of PSI genes induced under far-red light. These results indicate that Chl f functions to harvest the far-red light and enhance uphill energy transfer, and changes in the gene sequences are essential for the binding of Chl f.
Chlorophylls are magnesium-tetrapyrrole molecules that play essential roles in photosynthesis. All chlorophylls have similar five-membered ring structures, with variations in the side chains and/or ...reduction states. Formyl group substitutions on the side chains of chlorophyll a result in the different absorption properties of chlorophyll b, chlorophyll d, and chlorophyll f. These formyl substitution derivatives exhibit different spectral shifts according to the formyl substitution position. Not only does the presence of various types of chlorophylls allow the photosynthetic organism to harvest sunlight at different wavelengths to enhance light energy input, but the pigment composition of oxygenic photosynthetic organisms also reflects the spectral properties on the surface of the Earth. Two major environmental influencing factors are light and oxygen levels, which may play central roles in the regulatory pathways leading to the different chlorophylls. I review the biochemical processes of chlorophyll biosynthesis and their regulatory mechanisms.
Chlorophyll fluorescence is a non-invasive measurement of photosystem II (PSII) activity and is a commonly used technique in plant physiology. The sensitivity of PSII activity to abiotic and biotic ...factors has made this a key technique not only for understanding the photosynthetic mechanisms but also as a broader indicator of how plants respond to environmental change. This, along with low cost and ease of collecting data, has resulted in the appearance of a large array of instrument types for measurement and calculated parameters which can be bewildering for the new user. Moreover, its accessibility can lead to misuse and misinterpretation when the underlying photosynthetic processes are not fully appreciated. This review is timely because it sits at a point of renewed interest in chlorophyll fluorescence where fast measurements of photosynthetic performance are now required for crop improvement purposes. Here we help the researcher make choices in terms of protocols using the equipment and expertise available, especially for field measurements. We start with a basic overview of the principles of fluorescence analysis and provide advice on best practice for taking pulse amplitude-modulated measurements. We also discuss a number of emerging techniques for contemporary crop and ecology research, where we see continual development and application of analytical techniques to meet the new challenges that have arisen in recent years. We end the review by briefly discussing the emerging area of monitoring fluorescence, chlorophyll fluorescence imaging, field phenotyping, and remote sensing of crops for yield and biomass enhancement.
PDF
