Net heterotrophy in High Arctic first-year and multi-year spring sea ice

The net productivity of sea ice is determined by the physical and geochemical characteristics of the ice–ocean system and the activity of organisms inhabiting the ice. Differences in habitat suitability between first-year and multi-year sea ice can affect the ice algal community composition and acclimation state, introducing considerable variability to primary production within each ice type. In this study, we characterized the biogeochemical variability between adjacent first-year and multi-year sea ice floes in the Lincoln Sea of the Canadian High Arctic, during the May 2018 Multidisciplinary Arctic Program—Last Ice sampling campaign. Combining measurements of transmitted irradiance from a remotely operated underwater vehicle with laboratory-based oxygen optode incubations, this work shows widespread heterotrophy (net oxygen uptake) in the bottom 10 cm of both ice types, particularly in thick multi-year ice (>2.4 m) and early morning of the 24-h day. Algal acclimation state and species composition varied between ice types despite similar net community production due to widespread light and nutrient limitation. The first-year ice algal community was increasingly dominated over spring by the potentially toxin-producing genus Pseudonitzschia that was acclimated to high and variable light conditions characteristic of a thinner ice habitat with mobile snow cover. In comparison, the multi-year ice harbored more shade-acclimated algae of mixed composition. This work highlights the potential for heterotrophy in sea ice habitats of the High Arctic, including first measurements of such O2-uptake in multi-year ice floes. Observed differences in photophysiology between algae of these sea ice types suggests that a shift toward higher light availability and a younger sea ice cover with climate change does not necessarily result in a more productive system. Instead, it may favor future sea ice algal communities of different species composition, with lower photosynthetic potential but greater resilience to stronger and more variable light conditions.

Research on Stability of Gray Value of Excited-State Fluorescent Oil Film Based on Variable Light Vector Angle

In global skin-friction measurement of aircraft, the fluorescent oil film method can characterize the distribution of skin friction well. However, in an actual wind tunnel test, the wing of the aircraft will inevitably produce corresponding vibrations due to the influence of wind, which will change the relative position between fluorescent oil film and UV (ultraviolet) excitation light source (position fixed). This also directly affects gray value imaging of fluorescent oil films. Based on this, a mathematical model is established to judge the stability of the gray value of fluorescent oil film in this vibrational environment; then, the model can be solved to obtain the vibrational range constraint that enables the gray value of fluorescent oil film to be stabilized. In order to simplify the calculation process, the light vector angle is used to describe the constraint, which also makes the results more intuitive. Through experimental analysis and demonstration, the prediction accuracy of this model can reach 95.61%, which has certain practical engineering application significance.

Soluble Expression of Small Antibody Fragments against PD-L1 Using Escherichia coli with High Yield and Purity

Programmed death-ligand 1 (PD-L1) is a surface protein overexpressed in tumor cells. Recently, targeted therapy using PD-L1 antibodies to reconstitute the antitumor activity of T cells has received considerable attention as a cancer treatment. Among the several types of anti-PD-L1 antibodies, small-sized antibody fragments are useful agents to block PD-L1 for experimental and therapeutic purposes owing to their high penetration efficacy toward dense tumor cells. Herein, we expressed and purified recombinant single chain fragment of variable domain, variable heavy chain, and variable light chain, against PD-L1 in a soluble form using Escherichia coli, resulting in their high yield and high purity. We confirmed the antigen-binding efficiency of these antibody fragments, which showed antigen concentration-dependent responses. These results suggest that these small antibody fragments can serve as new agents for blocking or detecting PD-L1.

Acclimation of Photosynthesis to Changes in the Environment Results in Decreases of Oxidative Stress in Arabidopsis thaliana

The dynamic acclimation of photosynthesis plays an important role in increasing the fitness of a plant under variable light environments. Since acclimation is partially mediated by a glucose-6-phosphate/phosphate translocator 2 (GPT2), this study examined whether plants lacking GPT2, which consequently have defective acclimation to increases in light, are more susceptible to oxidative stress. To understand this mechanism, we used the model plant Arabidopsis thaliana [accession Wassilewskija-4 (Ws-4)] and compared it with mutants lacking GPT2. The plants were then grown at low light (LL) at 100 μmol m−2 s−1 for 7 weeks. For the acclimation experiments, a set of plants from LL was transferred to 400 μmol m−2 s−1 conditions for 7 days. Biochemical and physiological analyses showed that the gpt2 mutant plants had significantly greater activity for ascorbate peroxidase (APX), guiacol peroxidase (GPOX), and superoxide dismutase (SOD). Furthermore, the mutant plants had significantly lower maximum quantum yields of photosynthesis (Fv/Fm). A microarray analysis also showed that gpt2 plants exhibited a greater induction of stress-related genes relative to wild-type (WT) plants. We then concluded that photosynthetic acclimation to a higher intensity of light protects plants against oxidative stress.

Impaired photoprotection in Phaeodactylum tricornutum KEA3 mutants reveals the proton regulatory circuit of diatoms light acclimation

Diatoms are amongst the most successful clades of oceanic phytoplankton, significantly contributing to photosynthesis on Earth. Their ecological success likely stems from their ability to acclimate to changing environmental conditions, including e.g. variable light intensity. Diatoms are outstanding at dissipating light energy exceeding the maximum photosynthetic electron transfer (PET) capacity of via Non Photochemical Quenching (NPQ). While the molecular effectors of this process, as well as the role of the Proton Motive Force (PMF) in its regulation are known, the putative regulators of the PET/PMF relationship in diatoms remain unidentified. Here, we demonstrate that the H+/K+ antiporter KEA3 is the main regulator of the coupling between PMF and PET in the model diatom Phaeodactylum tricornutum. By controlling the PMF, it modulates NPQ responses at the onset of illumination, during transients and in steady state conditions. Under intermittent light KEA3 absence results in reduced fitness. Using a parsimonious model including only two components, KEA3 and the diadinoxanthin de-epoxidase, we can describe most of the feedback loops observed between PET and NPQ. This two-components regulatory system allows for efficient responses to fast (minutes) or slow (e.g. diel) changes in light environment, thanks to the presence of a regulatory Ca2+-binding domain in KEA3 that controls its activity. This circuit is likely finely tuned by the NPQ effector proteins LHCX, providing diatoms with the required flexibility to thrive in different ocean provinces.One sentence summaryThe author(s) responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (https://academic.oup.com/plcell/pages/General-Instructions) is Giovanni Finazzi.

An inexpensive setup for robust activity tracking in small animals: Portable Locomotion Activity Monitor (pLAM)

Advances in computer vision and deep learning have automated animal behaviour studies that previously required tedious manual input. However, tracking activity of small and fast flying animals remains a hurdle, especially in a field setting with variable light conditions. Commercial locomotor activity monitors (LAMs) can be expensive, closed source, and generally limited to laboratory settings.Here, we present a portable locomotion activity monitor (pLAM), a mobile activity detector to quantify small animal circadian activity. Our setup uses inexpensive components, is based on open-source motion tracking software, and is easy to assemble and use in the field. It runs off-grid, supports low-light tracking with infrared lights, and can implement arbitrary light cycle colours and brightnesses with programmable LEDs. We provide a user-friendly guide to assembling pLAM hardware and accessing its pre-configured software and guidelines for using it in other systems.We benchmarked pLAM for insects under various lab and field conditions, then compared results to a commercial activity detector. They offer broadly similar activity measures, but our setup captures flight and bouts of motion that are often missed by beam-breaking activity detection.pLAM will enable high-throughput quantification of small animal location and activity in a low-cost and accessible manner, crucial to studying behaviour that can help inform conservation and management decisions.

Rice Ear Counting Based on Image Segmentation and Establishment of a Dataset

The real-time detection and counting of rice ears in fields is one of the most important methods for estimating rice yield. The traditional manual counting method has many disadvantages: it is time-consuming, inefficient and subjective. Therefore, the use of computer vision technology can improve the accuracy and efficiency of rice ear counting in the field. The contributions of this article are as follows. (1) This paper establishes a dataset containing 3300 rice ear samples, which represent various complex situations, including variable light and complex backgrounds, overlapping rice and overlapping leaves. The collected images were manually labeled, and a data enhancement method was used to increase the sample size. (2) This paper proposes a method that combines the LC-FCN (localization-based counting fully convolutional neural network) model based on transfer learning with the watershed algorithm for the recognition of dense rice images. The results show that the model is superior to traditional machine learning methods and the single-shot multibox detector (SSD) algorithm for target detection. Moreover, it is currently considered an advanced and innovative rice ear counting model. The mean absolute error (MAE) of the model on the 300-size test set is 2.99. The model can be used to calculate the number of rice ears in the field. In addition, it can provide reliable basic data for rice yield estimation and a rice dataset for research.

The effect of fluctuating light on canopy photosynthesis: a focus on a chlorophyll-deficient Soybean mutant

<p>In natural environments plants are subjected to variable light conditions and therefore need an efficient regulatory system to regulate photosynthesis and the downstream metabolism. Most of the measurements available are taken at steady state and at leaf level but those may overestimate total carbon uptake in a more dynamic environment. Furthermore, some plants may be more adapted than others to deal with light fluctuations and therefore is difficult to draw general conclusions. We then grew a commercial soybean variety and a chlorophyll deficient mutant in a recently developed growth chamber system (DYNAMISM) which allowed to obtain instantaneous gas exchange data at canopy level for several weeks. By doing so we could investigate both short term responses and long term adaptations to light dynamic conditions of the two varieties. At steady state, chlorophyll deficient crops are thought to have a similar or even a higher photosynthetic rate compared to the green wildtypes, enhanced by a higher light transmittance throughout the canopy. But little is known about how they respond to fluctuations in light. The two varieties were grown either in fluctuating (F) or non-fluctuating (NF) light conditions to evaluate how variable light would affect biomass accumulation. Two different light treatments were applied, low light (LL) and high light (HL) with different light intensities and amplitude of fluctuations. The LL treatment did not entail any difference among F and NF in both varieties. The chlorophyll-deficient mutant was instead found to be susceptible to the fluctuations of light in the HL treatment, by accumulating less biomass. It is hypothesised that this might be due to its longer non‐photochemical quenching relaxation time  in light transitions, but other acclimatation mechanisms need to be investigated.</p>