Photosynthesis Research最新文献

Dichotomosiphon tuberosus is one of the Bryopsidales, a siphonous, unicellular multinucleate ulvophyte. Bryopsidales typically occur in the ocean and contain unique carbonyl carotenoids siphonaxanthin (Sx) and its ester siphonein (Sn) in their major light-harvesting pigment-protein complexes, allowing them to utilize the green light available in the deep ocean for photosynthesis. However, unlike other Bryopsidales, D. tuberosus occurs in fresh water and is reported to contain Sn but not Sx. D. tuberosus inhabits deep lakes around the world, but in Okinawa, Japan, it inhabits very shallow waterways. Here, we measured the photosynthetic capacity of D. tuberosus collected from Okinawa waterway and compared it with another intertidal Bryopsidale Codium fragile. D. tuberosus had higher photosynthetic electron transport capacity and stronger non-photochemical quenching than C. fragile, consistent with the brighter growth environments for D. tuberosus than C. fragile. We also measured the absorption spectra and the pigment compositions within the photosynthetic pigment-protein complexes from D. tuberosus. Green light absorption of each complex in D. tuberosus was weaker than that in C. fragile. In contrast, Chl b absorption in LHCII was stronger in D. tuberosus than in C. fragile, whereas the opposite was true in photosystems. This implies that a large proportion of the irradiated energy is absorbed by LHCII complex and quenched more efficiently. Our results indicate that the photosynthetic capacity of D. tuberosus is further optimized for higher light environments compared with C. fragile.

In plants, the photo-inhibitory effects of incident lights on the light-harvesting complexes are balanced by photoprotective mechanisms to maintain photosynthesis. With increasing air CO₂ concentrations and temperatures, the balance can tilt either way, with unpredictable consequences for biomass assimilated through photosynthesis. As such, it is critical to assess the photosynthetic responses of crop plants growing in future climates to light for developing strategies for sustaining food production. This study evaluated changes in photosynthetic and chlorophyll fluorescence responses to light intensities in peanuts (Arachis hypogaea L) acclimated to projected future climates by Global Circulation Models (GCM). The plants were grown in plant growth chambers under three climate conditions (CC): (1) ambient air [CO₂] and ambient temperature [Ta] (CC1), (2) [CO₂] at 570 ppm and Ta + 3⁰ C (CC2 climate possible in 2050), and (3) [CO₂] at 780 ppm and Ta + 5⁰C (CC3, climate possible in 2080). Plants growing under all three climates enhanced photosynthetic rates (A) with light intensities from 0 to 1500 µ mol m^- 2 s^- 1 but decreased afterward. Compared to CC1, plants growing under CC2 and CC3 reduced electron transport rates (ETR), A, and transpiration (Tr) between 48 and 190%, 52 and 65%, and 22 and 24%, respectively. Concurrently, the quantum efficiency of photosystem II (ФPS2) was reduced by 88-200% and photochemical quenching (qP) by 55-170%. Non-photochemical quenching increased with increasing light levels from 200 to 1500 µmol m⁻² s⁻¹ and decreased afterward. Results indicated the possibility of reduced photosynthetic efficiencies under CC2 and CC3, which would significantly reduce biomass production in future climates. Gaining insight into these impacts can help understand plant's ability to adapt and assist in developing adaptive strategies for sustainable peanut farming.

Light-driven water oxidation by photosystem II sustains life on Earth by providing the electrons and protons for the reduction of CO₂ to carbohydrates and the molecular oxygen we breathe. The inorganic core of the oxygen evolving complex is made of the earth-abundant elements manganese, calcium and oxygen (Mn₄CaO₅ cluster), and is situated in a binding pocket that is connected to the aqueous surrounding via water-filled channels that allow water intake and proton egress. Recent serial crystallography and infrared spectroscopy studies performed with PSII isolated from Thermosynechococcus vestitus (T. vestitus) support that one of these channels, the O1 channel, facilitates water access to the Mn₄CaO₅ cluster during its S₂→S₃ and S₃→S₄→S₀ state transitions, while a subsequent CryoEM study concluded that this channel is blocked in the cyanobacterium Synechocystis sp. PCC 6803, questioning the role of the O1 channel in water delivery. Employing site-directed mutagenesis we modified the two O1 channel bottleneck residues D1-E329 and CP43-V410 (T. vestitus numbering) and probed water access and substrate exchange via time resolved membrane inlet mass spectrometry. Our data demonstrates that water reaches the Mn₄CaO₅ cluster via the O1 channel in both wildtype and mutant PSII. In addition, the detailed analysis provides functional insight into the intricate protein-water-cofactor network near the Mn₄CaO₅ cluster that includes the pentameric, near planar 'water wheel' of the O1 channel.

The ability of diatoms to adapt to variable light conditions such as photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) is crucial for their survival and ecological role. The study aimed to investigate how different doses of UVR regulate the photoprotection mechanism in Phaeodactylum tricornutum. Five treatments were established: Control (PAR only), PAR + UVR D_6h (17.5 W m^- 2, 6 h, 378 KJ m^- 2), PAR + UVR 2D_6h (35 W m^- 2, 6 h, 756 KJ m^- 2), PAR + UVR 2D_12h (17.5 W m^- 2, 12 h, 756 KJ m^- 2), and PAR + UVR 4D_12h (35 W m^- 2, 12 h, 1.512 KJ m^- 2). The growth of P. tricornutum was significantly affected by UVR doses, with a growth pattern of 42-55% below the control (PAR only). Increasing the UVR dose also had negative effects on photosynthesis parameters and the levels of chlorophyll-a and fucoxanthin. The de-epoxidation state showed a high rate in treatments subjected to higher UVR doses, promoting an attempt to activate cellular protection mechanisms. In the transcriptional genes related to the xanthophyll cycle, a reduction in transcript levels of ZEP1 and ZEP2 genes was observed in PAR + UVR treatments, including a reduction up to 75% at 72 h of exposure. Also, an increase in transcript levels of VDE and VDL1 genes was observed for treatments with the same UVR dose, reaching about 9-fold increase for the 2D_12h dose and 10-fold increase for the 2D_6h dose, both at 72 h, suggesting a modification in the cell's ability to respond to UVR light stress.

In vivo chlorophyll fluorescence has long been known to be intimately related to photosynthesis, being the basis of widespread and sophisticated instrumentation. Although easily observed in plant extracts or using epifluorescence or confocal microscopes, chlorophyll fluorescence is seldom observed in macroscopic samples, such as plant leaves of macroalgae thalli. This work presents a 'chlorophyll fluoroscope', a device that allows the direct observation of the fluorescence emitted in vivo by large samples. The chlorophyll fluoroscope is easy to construct and operate, comprising inexpensive 3D-printed parts and off-the-shelve components. It is primarily intended for use in teaching and science demonstration events while having the potential to interest those who are aware of chlorophyll fluorescence yet often have never observed the phenomenon.

Soybean is a short-day crop and the long-duration variety takes 120 days for maturity. A protocol for rapid generation advancement in soybean breeding is worthwhile keeping in view its utility. The study emphasizes standardisation of physical conditions, especially using warm white and cool white light-emitting diodes to hasten flowering and pod setting in soybean (DS9712 genotype). Complete open flowers were obtained with a 16 L/8D (dark/light) photoperiod in 30 days. The results also highlighted the application of interventions of physical conditions and inputs, especially during the reproductive phase to shorten the seed-to-seed generation time by around 15 days in a low-cost method for soybean breeding. Breeding will be revolutionised in case economic speed breeding is combined with modern breeding technologies, thereby resulting in more generations per year.

In cyanobacteria and red algae, allophycocyanin (APC), as well as other phycobiliproteins, is involved in the energy transfer of photosystems. Since APC is a potent fluorescent protein for imaging and biomedical applications, it is necessary to obtain purified protein in large quantities, which is currently possible by biosynthesis in bacterial systems. Here we emphasize the challenges of obtaining the trimeric form of the protein from α-APC and β-APC subunits of allophycocyanin in vitro. This approach allowed us to study the individual subunits and to perform assembly of allophycocyanin trimers in vitro. Using different spectroscopic techniques, we detected the heterogeneity of the synthesized β-APC and showed the possibility that not only holo-forms may be involved in trimer formation. Data allowed us to provide additional arguments in favor of excitonic coupling of chromophores in APC trimers.

Chlorophyll (Chl) f production expands oxygenic photosynthesis of some cyanobacteria into the far-red light (FRL) region through reconstructed FRL-allophycocyanin (APC) cores and Chl f-containing photosystems. Presently, a unicellular cyanobacterium was isolated for studying FRL photoacclimation (FaRLiP) and classified as a new species Altericista leshanensis. It uses additional Chl f and FRL-APC cores, with retained white light (WL)-phycobiliproteins to thrive FRL conditions. Marker-less deletion of FaRLiP-apcE2 gene was constructed using CRISPR-Cpf1 system. This genetic manipulation has no significant effects on the expression of genes in the FaRLiP gene cluster, including adjacent apc genes under FRL conditions. The function-loss mutant cells cannot assemble FRL-APC cores, and show the decreased growth rate and Chl f production under FRL conditions. Interestingly, the expression levels of phycocyanin (PC) subunits (cpc) and photosystem II D1 proteins (psbA2) are significantly increased in mutant cells under FRL conditions. These results suggest that FRL acclimation in the mutant cells has a different photosynthetic apparatus due to the lack of FRL-APC cores. The alternative strategy of FaRLiP provides additional evidence of flexible pathways towards the potential application of Chl f and associated biotechnology.

Advancements in artificial intelligence (AI) have greatly benefited plant phenotyping and predictive modeling. However, unrealized opportunities exist in leveraging AI advancements in model parameter optimization for parameter fitting in complex biophysical models. This work developed novel software, PhoTorch, for fitting parameters of the Farquhar, von Caemmerer, and Berry (FvCB) biochemical photosynthesis model based on the parameter optimization components of the popular AI framework PyTorch. The primary novelty of the software lies in its computational efficiency, robustness of parameter estimation, and flexibility in handling different types of response curves and sub-model functional forms. PhoTorch can fit both steady-state and non-steady-state gas exchange data with high efficiency and accuracy. Its flexibility allows for optional fitting of temperature and light response parameters, and can simultaneously fit light response curves and standard $A/C_i$ curves. These features are not available within presently available $A/C_i$ curve fitting packages. Results illustrated the robustness and efficiency of PhoTorch in fitting $A/C_i$ curves with high variability and some level of artifacts and noise. PhoTorch is more than four times faster than benchmark software, which may be relevant when processing many non-steady-state $A/C_i$ curves with hundreds of data points per curve. PhoTorch provides researchers from various fields with a reliable and efficient tool for analyzing photosynthetic data. The Python package is openly accessible from the repository: https://github.com/GEMINI-Breeding/photorch .