Photosynthesis Research最新文献

Organic bilayers or amorphous silica films of a few nanometer thickness featuring embedded molecular wires offer opportunities for chemically separating while at the same time electronically connecting photo- or electrocatalytic components. Such ultrathin membranes enable the integration of components for which direct coupling is not sufficiently efficient or stable. Photoelectrocatalytic systems for the generation or utilization of renewable energy are among the most prominent ones for which ultrathin separation layers open up new approaches for component integration for improving efficiency. Recent advances in the assembly and spectroscopic, microscopic, and photoelectrochemical characterization have enabled the systematic optimization of the structure, energetics, and density of embedded molecular wires for maximum charge transfer efficiency. The progress enables interfacial designs for the nanoscale integration of the incompatible oxidation and reduction catalysis environments of artificial photosystems and of microbial (or biomolecular)-abiotic systems for renewable energy.

The quality of light is an important abiotic factor that affects the growth and development of green plants. Ultraviolet, red, blue, and far-red light all have demonstrated roles in regulating green plant growth and development, as well as light morphogenesis. However, the mechanism underlying photosynthetic organism responses to green light throughout the life of them are not clear. In this study, we exposed the unicellular green alga Chlamydomonas reinhardtii to green light and analyzed the dynamics of transcriptome changes. Based on the whole transcriptome data from C. reinhardtii, a total of 9974 differentially expressed genes (DEGs) were identified under green light. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that these DEGs were mainly related to “carboxylic acid metabolic process,” “enzyme activity,” “carbon metabolism,” and “photosynthesis and other processes.” At the same time, 253 differentially expressed long non-coding RNAs (DELs) were characterized as green light responsive. We also made a detailed analysis of the responses of photosynthesis- and pigment synthesis-related genes in C. reinhardtii to green light and found that these genes exhibited obvious dynamic expression. Lastly, we constructed a co-expression regulatory network, comprising 49 long non-coding RNAs (lncRNAs) and 20 photosynthesis and pigment related genes, of which 9 mRNAs were also the predicted trans/cis-targets of 8 lncRNAs, these results suggested that lncRNAs may affect the expression of mRNAs related to photosynthesis and pigment synthesis. Our findings give a preliminary explanation of the response mechanism of C. reinhardtii to green light at the transcriptional level.

Abstract

Inhibitory analysis is a useful tool for studying cytochrome b₆f complex in the photosynthetic electron transport chain. Here, we examine the inhibitory efficiency of two widely used inhibitors of the plastoquinol oxidation in the cytochrome b₆f complex, namely 2,4-dinitrophenyl ether of 2-iodo-4-nitrothymol (DNP-INT) and 2,5-dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB). Using isolated thylakoids from pea and arabidopsis, we demonstrate that inhibitory activity of DNP-INT and DBMIB is enhanced by increasing irradiance, and this effect is due to the increase in the rate of electron transport. However, the accumulation of protons in the thylakoid lumen at low light intensity has opposite effects on the inhibitory activity of DNP-INT and DBMIB, namely increasing the activity of DNP-INT and restricting the activity of DBMIB. These results allow for the refinement of the conditions under which the use of these inhibitors leads to the complete inhibition of plastoquinol oxidation in the cytochrome b₆f complex, thereby broadening our understanding of the operation of the cytochrome b₆f complex under conditions of steady-state electron transport.

The chlorophyllide a oxygenase (CAO) plays a crucial role in the biosynthesis of chlorophyll b (Chl b). In the moss Physcomitrium patens (P. patens), two distinct gene copies, PpCAO1 and PpCAO2, are present. In this study, we investigate the differential expression of these CAOs following light exposure after a period of darkness (24 h) and demonstrate that the accumulation of Chl b is only abolished when both genes are knocked out. In the ppcao1cao2 mutant, most of the antenna proteins associated with both photosystems (PS) I and II are absent. Despite of the existence of LHCSR proteins and zeaxanthin, the mutant exhibits minimal non-photochemical quenching (NPQ) capacity. Nevertheless, the ppcao1cao2 mutant retains a certain level of pseudo-cyclic electron transport to provide photoprotection for PSI. These findings shed light on the dual dependency of Chl b synthesis on two CAOs and highlight the distinct effects of Chl b deprival on PSI and PSII core complexes in P. patens, a model species for bryophytes.

Quantifying water use efficiency, and the impact of stomata on CO₂ uptake are pivotal in physiology and efforts to improve crop yields. Although tempting, relying on regression slopes from assimilation-stomatal conductance plots to estimate water use efficiency or stomatal control over assimilation is erroneous. Through numerical simulations, I substantiate this assertion. I propose the term 'instantaneous transpiration efficiency' for the assimilation-to-transpiration ratio to avoid confusion with 'intrinsic water use efficiency' which refers to the assimilation-to-stomatal conductance ratio, and recommend to compute both metrics for each gas exchange data point.

Light availability effects on canopy-level carbon balance constitute an especially difficult issue to address, owing to the strong spatial and temporal changes of the light environment within the canopy. One of the least explored aspects in relation to light environment is the interaction between leaf angle and leaf anatomy. The inclination of the leaf may affect the distribution of light between the adaxial and abaxial surface. The purpose of this study is determining the proportions of the leaf area receiving light from the abaxial side in branches of isolated trees in three Mediterranean oaks, as well as the photosynthetic responses to light under adaxial and abaxial illumination. The proportions of the leaf area illuminated from below were low for sun incidence angles near 0° with respect to the main axis of the branch. However, for sun incidence angles about 45°, the proportion of leaves receiving abaxial illumination was considerable. PPFD levels on the sunlit part of the abaxial surface were always lower than those in the upper leaf side, as a consequence of the lower projection efficiency for the leaves facing the sun by the lower side. Light absorptance was also lower on the abaxial side. The differences between both sides of the leaf tended to be stronger for thicker, longer-living leaves. We conclude that mean C assimilation of the canopy is significantly decreased by the presence of leaves facing the sun by the lower side and that this decrease is stronger in evergreen species with thicker leaves.

Warming driven by the accumulation of greenhouse gases in the atmosphere is irreversible over at least the next century, unless practical technologies are rapidly developed and deployed at scale to remove and sequester carbon dioxide from the atmosphere. Accepting this reality highlights the central importance for crop agriculture to develop adaptation strategies for a warmer future. While nearly all processes in plants are impacted by above optimum temperatures, the impact of heat stress on photosynthetic processes stand out for their centrality. Here, we review transgenic strategies that show promise in improving the high-temperature tolerance of specific subprocesses of photosynthesis and in some cases have already been shown in proof of concept in field experiments to protect yield from high temperature-induced losses. We also highlight other manipulations to photosynthetic processes for which full proof of concept is still lacking but we contend warrant further attention. Warming that has already occurred over the past several decades has had detrimental impacts on crop production in many parts of the world. Declining productivity presages a rapidly developing global crisis in food security particularly in low income countries. Transgenic manipulation of photosynthesis to engineer greater high-temperature resilience holds encouraging promise to help meet this challenge.

One of the reasons for the high efficiency and selectivity of biological catalysts arise from their ability to control the pathways of substrates and products using protein channels, and by modulating the transport in the channels using the interaction with the protein residues and the water/hydrogen-bonding network. This process is clearly demonstrated in Photosystem II (PS II), where its light-driven water oxidation reaction catalyzed by the Mn₄CaO₅ cluster occurs deep inside the protein complex and thus requires the transport of two water molecules to and four protons from the metal center to the bulk water. Based on the recent advances in structural studies of PS II from X-ray crystallography and cryo-electron microscopy, in this review we compare the channels that have been proposed to facilitate this mass transport in cyanobacteria, red and green algae, diatoms, and higher plants. The three major channels (O1, O4, and Cl1 channels) are present in all species investigated; however, some differences exist in the reported structures that arise from the different composition and arrangement of membrane extrinsic subunits between the species. Among the three channels, the Cl1 channel, including the proton gate, is the most conserved among all photosynthetic species. We also found at least one branch for the O1 channel in all organisms, extending all the way from Ca/O1 via the 'water wheel' to the lumen. However, the extending path after the water wheel varies between most species. The O4 channel is, like the Cl1 channel, highly conserved among all species while having different orientations at the end of the path near the bulk. The comparison suggests that the previously proposed functionality of the channels in T. vestitus (Ibrahim et al., Proc Natl Acad Sci USA 117:12624-12635, 2020; Hussein et al., Nat Commun 12:6531, 2021) is conserved through the species, i.e. the O1-like channel is used for substrate water intake, and the tighter Cl1 and O4 channels for proton release. The comparison does not eliminate the potential role of O4 channel as a water intake channel. However, the highly ordered hydrogen-bonded water wire connected to the Mn₄CaO₅ cluster via the O4 may strongly suggest that it functions in proton release, especially during the S₀ → S₁ transition (Saito et al., Nat Commun 6:8488, 2015; Kern et al., Nature 563:421-425, 2018; Ibrahim et al., Proc Natl Acad Sci USA 117:12624-12635, 2020; Sakashita et al., Phys Chem Chem Phys 22:15831-15841, 2020; Hussein et al., Nat Commun 12:6531, 2021).