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High-throughput measurements of photosynthesis of plants grown under various conditions may provide important insights into the plasticity of the photosynthetic performance of plants. Remote sensing of photosynthetic activity is the next generation of fast scanning techniques, enabling high-throughput photosynthesis measurements under controlled conditions. We hypothesized that by measuring SIF simultaneously with whole-plant water relations in a standardized controlled drought experiment, we would be able to quantify photosynthetic activity and to detect water stress at an early stage. A functional-phenotyping platform was used to apply the controlled drought treatment and to monitor the growth and water balance of tomato introgression lines (ILs). A new SIF-derived index, electron transport rate (RS-ETRi), was found to be negatively correlated with whole-plant stomatal conductance (Gsc) under non-stressed conditions. No significant relationships were found between SIF and plant biomass or Gsc. SIF687responded to drought earlier than any of the other measured vegetation indices. SIF based indices could not differentiate between introgressed lines of tomato; whereas differences between Introgression Lines were clearly identified by the water-relations measurements. We concluded that SIF did not provide any advantage over commonly used methods for detecting physiological differences between the Introgression Lines. Overall, although SIF plays a significant role in photosynthesis, the relationship between SIF and photosynthesis is complex and we believe it would be an oversimplification to use SIF to quantify photosynthetic activity on close canopy spatial resolution level.

We present work of our COST Action on "Understanding and exploiting the impacts of low pH on micro-organisms". First, we summarise a workshop held at the European Federation of Biotechnology meeting on Microbial Stress Responses (online in 2020) on "Industrial applications of low pH stress on microbial bio-based production", as an example of an initiative fostering links between pure and applied research. We report the outcomes of a small survey on the challenging topic of developing links between researchers working in academia and industry that show that, while people in different sectors strongly support such links, barriers remain that obstruct this process. We present the thoughts of an expert panel held as part of the workshop above, where people with experience of collaboration between academia and industry shared ideas on how to develop and maintain links. Access to relevant information is essential for research in all sectors, and because of this we have developed, as part of our COST Action goals, two resources for the free use of all researchers with interests in any aspects of microbial responses to low pH. These are (1) a comprehensive database of references in the literature on different aspects of acid stress responses in different bacterial and fungal species, and (2) a database of research expertise across our network. We invite the community of researchers working in this field to take advantage of these resources to identify relevant literature and opportunities for establishing collaborations.

Microbes from the three domains of life, Bacteria, Archaea, and Eukarya, share the need to sense and respond to changes in the external and internal concentrations of protons. When the proton concentration is high, acidic conditions prevail and cells must respond appropriately to ensure that macromolecules and metabolic processes are sufficiently protected to sustain life. While, we have learned much in recent decades about the mechanisms that microbes use to cope with acid, including the unique challenges presented by organic acids, there is still much to be gained from developing a deeper understanding of the effects and responses to acid in microbes. In this perspective article, we survey the key molecular mechanisms known to be important for microbial survival during acid stress and discuss how this knowledge might be relevant to microbe-based applications and processes that are consequential for humans. We discuss the research approaches that have been taken to investigate the problem and highlight promising new avenues. We discuss the influence of acid on pathogens during the course of infections and highlight the potential of using organic acids in treatments for some types of infection. We explore the influence of acid stress on photosynthetic microbes, and on biotechnological and industrial processes, including those needed to produce organic acids. We highlight the importance of understanding acid stress in controlling spoilage and pathogenic microbes in the food chain. Finally, we invite colleagues with an interest in microbial responses to low pH to participate in the EU-funded COST Action network called EuroMicropH and contribute to a comprehensive database of literature on this topic that we are making publicly available. info:eu-repo/semantics/publishedVersion

Plants transpire water through their tissues in order to move nutrients and water to the cells. Transpiration includes various mechanisms, primarily stomata movement, which controls the rate of CO2 and water vapor exchange between the tissues and the atmosphere. Assessment of stomatal conductance is available for gas exchange techniques at leaf level, yet these techniques are not scalable to the whole plant let alone a large vegetation area. Hyperspectral reflectance spectroscopy, which acquires hundreds of bands in a single scan, may capture a glimpse of the crop’s physiological activity and therefore meet the scalability challenge. In this study, classic chemometric analyses are used alongside advanced statistical learning algorithms in order to identify stomatal conductance cues in hyperspectral measurements of cotton plants experiencing a gradient of irrigation. Random forest of regression trees identified 23 wavelengths related to both structural properties of the plant as well as water content. Partial least squares regression succeeded in relating these wavelengths to stomatal conductance, but only partially (R2 < 0.2). An artificial neural network algorithm reported an R2 = 0.54 with an 89% error-free performance on the same data subset. This study discusses implementation of machine learning methodologies as a benchmark for deeper analysis of spectral information, such as required when searching for plant physiology-related attenuations embedded within reflectance spectra.

Photosynthesis performance can be assessed quantitatively with light response curves. These curves record the Electron Transport Rate (ETR) as a function of light intensity. Then, statistical fit on these curves parameterize light use efficiency, maximum photosynthetic activity and the reaction of the apparatus to stress. While this technique is performed with portable fluorometers in field conditions, it is difficult to scale it to the canopy level. The Fraunhofer line discrimination technique, which detects fluorescence signals emitted during photosynthesis, is a promising method to assess photosynthetic performance of canopies. In this study, we define a remote sensing ETR index based on a combination of three parameters: sun-induced fluorescence, normalized differential vegetation index and light intensity. Two representatives of C3 and C4 photosynthesis, L. sativa and Z. mays, experienced a fertilization concentrations gradient. ETR increased with light intensity in both crops. In L. sativa, ETR assumed a linear relationship between the photosynthetic activity and light intensity, with a correlation of R2 = 0.99 to the portable fluorometer. Additional parametrization revealed a resilience of its reaction centers to photoinhibition in maximum light intensities. When Z. mays experienced open field conditions, ETR correlated with the plant’s status. While the results of this study are promising, the index still requires validation in terms of temporal track and spatial variability.

Synechocystis sp. PCC6803 actively uptake inorganic carbon to elevate the carbon dioxide concentration around their Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) enzyme. The mechanism is comprised of a set of enzymatic complexes which act in an orchestrated manner to transfer extracellular dissolved inorganic carbon into the cell and concentrate it within a specialized compartment. NADPH dehydrogenase-1 is the first operational super-complex in light conditions and, therefore, allows a direct estimation of carbon flux into the cell, albeit before photosynthesis and the concentrating mechanism reach a chemical steady-state condition. We calculated the uptake rate during this period by fitting a nonlinear function to the sharp decline in the CO 2 gas exchange profile recorded with membrane inlet mass spectrometry, considering the constant change in rate during this step. We estimate the carbon dioxide uptake rates and pool sizes, showing that these values correspond to previously reported steady state rates in the literature. During the investigation, we reveal new properties of the uptake mechanism. At pH lower than six, the enzymatic complex responsible for the CO 2 uptake becomes inactive. Its activity recovers within minutes when attenuating the pH within the cell or elevating it back at or above pH 6.0 outside the cell, a characteristic which seems to be conserved in activity in Symbiodinium microadriaticum , Isochrysis galbana , Phaeodactylum tricornutum and Emiliania huxleyi . We, therefore, suggest that within the carbon concentrating mechanism, CO 2 insertion processes can be deactivated when the organism faces pH 5.7.

Fridman, Svetlana ... et al.-- This is contribution number 54 of Tara Oceans.-- 8 pages, 4 figures, supplementary material https://dx.doi.org/10.1038/s41564-017-0002-9, Cyanobacteria are important contributors to primary production in the open oceans. Over the past decade, various photosynthesis-related genes have been found in viruses that infect cyanobacteria (cyanophages). Although photosystem II (PSII) genes are common in both cultured cyanophages and environmental samples , viral photosystem I (vPSI) genes have so far only been detected in environmental samples . Here, we have used a targeted strategy to isolate a cyanophage from the tropical Pacific Ocean that carries a PSI gene cassette with seven distinct PSI genes (psaJF, C, A, B, K, E, D) as well as two PSII genes (psbA, D). This cyanophage, P-TIM68, belongs to the T4-like myoviruses, has a prolate capsid, a long contractile tail and infects Prochlorococcus sp. strain MIT9515. Phage photosynthesis genes from both photosystems are expressed during infection, and the resultant proteins are incorporated into membranes of the infected host. Moreover, photosynthetic capacity in the cell is maintained throughout the infection cycle with enhancement of cyclic electron flow around PSI. Analysis of metagenomic data from the Tara Oceans expedition shows that phages carrying PSI gene cassettes are abundant in the tropical Pacific Ocean, composing up to 28% of T4-like cyanomyophages. They are also present in the tropical Indian and Atlantic Oceans. P-TIM68 populations, specifically, compose on average 22% of the PSI-gene-cassette carrying phages. Our results suggest that cyanophages carrying PSI and PSII genes are likely to maintain and even manipulate photosynthesis during infection of their Prochlorococcus hosts in the tropical oceans, This work was funded by a European Commission ERC Advanced Grant (no. 321647), the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/ under REA Grant Agreement No. 317184, an Israel Science Foundation grant (no. 580/10) and the Louis and Lyra Richmond Memorial Chair in Life Sciences to O.B., a European Commission ERC starting grant (no. 203406) to D.L. and the Technion’s Lorry I. Lokey Interdisciplinary Center for Life Sciences and Engineering and the Russell Berrie Nanotechnology Institute.

Background Hydrogen photo-production in green algae, catalyzed by the enzyme [FeFe]-hydrogenase (HydA), is considered a promising source of renewable clean energy. Yet, a significant increase in hydrogen production efficiency is necessary for industrial scale-up. We have previously shown that a major challenge to be resolved is the inferior competitiveness of HydA with NADPH production, catalyzed by ferredoxin-NADP+-reductase (FNR). In this work, we explored the in vivo hydrogen production efficiency of Fd-HydA, where the electron donor ferredoxin (Fd) is fused to HydA and expressed in the model organism Chlamydomonas reinhardtii. Results We show that once the Fd-HydA fusion gene is expressed in micro-algal cells of C. reinhardtii, the fusion enzyme is able to intercept photosynthetic electrons and use them for efficient hydrogen production, thus supporting the previous observations made in vitro. We found that Fd-HydA has a ~4.5-fold greater photosynthetic hydrogen production rate standardized for hydrogenase amount (PHPRH) than that of the native HydA in vivo. Furthermore, we provide evidence suggesting that the fusion protein is more resistant to oxygen than the native HydA. Conclusions The in vivo photosynthetic activity of the Fd-HydA enzyme surpasses that of the native HydA and shows higher oxygen tolerance. Therefore, our results provide a solid platform for further engineering efforts towards efficient hydrogen production in microalgae through the expression of synthetic enzymes. Electronic supplementary material The online version of this article (doi:10.1186/s13068-016-0601-3) contains supplementary material, which is available to authorized users.