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Frontiers in Plant Science 2022In this study, the differences in chlorophyll fluorescence transient (OJIP) and modulated 820 nm reflection (MR) of cucumber leaves were probed to demonstrate an insight...
In this study, the differences in chlorophyll fluorescence transient (OJIP) and modulated 820 nm reflection (MR) of cucumber leaves were probed to demonstrate an insight into the precise influence of melatonin (MT) on cucumber photosystems under low temperature stress. We pre-treated cucumber seedlings with different levels of MT (0, 25, 50, 100, 200, and 400 μmol · L) before imposing low temperature stress (10 °C/6 °C). The results indicated that moderate concentrations of MT had a positive effect on the growth of low temperature-stressed cucumber seedlings. Under low temperature stress conditions, 100 μmol · L (MT 100) improved the performance of the active photosystem II (PSII) reaction centers (PIabs), the oxygen evolving complex activity (OEC centers) and electron transport between PSII and PSI, mainly by decreasing the L-band, K-band, and G-band, but showed differences with different duration of low temperature stress. In addition, these indicators related to quantum yield and energy flux of PSII regulated by MT indicated that MT (MT 100) effectively protected the electron transport and energy distribution in the photosystem. According to the results of ≥ 1 and MR signals, MT also affected PSI activity. MT 100 decreased the minimal value of MR/MR and the oxidation rate of plastocyanin (PC) and PSI reaction center (P700) ( ), while increased △MR/MR and deoxidation rates of PC and P ( ). The loss of the slow phase of MT 200 and MT 400-treated plants in the MR kinetics was due to the complete prevention of electron movement from PSII to re-reduce the PC and P700 . These results suggest that appropriate MT concentration (100 μmol · L) can improve the photosynthetic performance of PS II and electron transport from primary quinone electron acceptor (Q) to secondary quinone electron acceptor (Q), promote the balance of energy distribution, strengthen the connectivity of PSI and PSII, improve the electron flow of PSII Q to PC and P from reaching PSI by regulating multiple sites of electron transport chain in photosynthesis, and increase the pool size and reduction rates of PSI in low temperature-stressed cucumber plants, All these modifications by MT 100 treatment promoted the photosynthetic electron transfer smoothly, and further restored the cucumber plant growth under low temperature stress. Therefore, we conclude that spraying MT at an appropriate concentration is beneficial for protecting the photosynthetic electron transport chain, while spraying high concentrations of MT has a negative effect on regulating the low temperature tolerance in cucumber.
PubMed: 36407604
DOI: 10.3389/fpls.2022.1029854 -
International Journal of Molecular... Oct 2022Cell surface receptors play essential roles in perceiving and processing external and internal signals at the cell surface of plants and animals. The receptor-like...
Cell surface receptors play essential roles in perceiving and processing external and internal signals at the cell surface of plants and animals. The receptor-like protein kinases (RLK) and receptor-like proteins (RLPs), two major classes of proteins with membrane receptor configuration, play a crucial role in plant development and disease defense. Although RLPs and RLKs share a similar single-pass transmembrane configuration, RLPs harbor short divergent C-terminal regions instead of the conserved kinase domain of RLKs. This RLP receptor structural design precludes sequence comparison algorithms from being used for high-throughput predictions of the RLP family in plant genomes, as has been extensively performed for RLK superfamily predictions. Here, we developed the RLPredictiOme, implemented with machine learning models in combination with Bayesian inference, capable of predicting RLP subfamilies in plant genomes. The ML models were simultaneously trained using six types of features, along with three stages to distinguish RLPs from non-RLPs (NRLPs), RLPs from RLKs, and classify new subfamilies of RLPs in plants. The ML models achieved high accuracy, precision, sensitivity, and specificity for predicting RLPs with relatively high probability ranging from 0.79 to 0.99. The prediction of the method was assessed with three datasets, two of which contained leucine-rich repeats (LRR)-RLPs from Arabidopsis and rice, and the last one consisted of the complete set of previously described Arabidopsis RLPs. In these validation tests, more than 90% of known RLPs were correctly predicted via RLPredictiOme. In addition to predicting previously characterized RLPs, RLPredictiOme uncovered new RLP subfamilies in the Arabidopsis genome. These include probable lipid transfer (PLT)-RLP, plastocyanin-like-RLP, ring finger-RLP, glycosyl-hydrolase-RLP, and glycerophosphoryldiester phosphodiesterase (GDPD, GDPDL)-RLP subfamilies, yet to be characterized. Compared to the only Arabidopsis GDPDL-RLK, molecular evolution studies confirmed that the ectodomain of GDPDL-RLPs might have undergone a purifying selection with a predominance of synonymous substitutions. Expression analyses revealed that predicted GDPGL-RLPs display a basal expression level and respond to developmental and biotic signals. The results of these biological assays indicate that these subfamily members have maintained functional domains during evolution and may play relevant roles in development and plant defense. Therefore, RLPredictiOme provides a framework for genome-wide surveys of the RLP superfamily as a foundation to rationalize functional studies of surface receptors and their relationships with different biological processes.
Topics: Animals; Plant Proteins; Arabidopsis; Plastocyanin; Bayes Theorem; Leucine; Plants; Protein Kinases; Receptors, Cell Surface; Machine Learning; Hydrolases; Phosphoric Diester Hydrolases; Lipids; Phylogeny
PubMed: 36293031
DOI: 10.3390/ijms232012176 -
Nature Plants Oct 2022Photosystem I (PSI) enables photo-electron transfer and regulates photosynthesis in the bioenergetic membranes of cyanobacteria and chloroplasts. Being a multi-subunit...
Photosystem I (PSI) enables photo-electron transfer and regulates photosynthesis in the bioenergetic membranes of cyanobacteria and chloroplasts. Being a multi-subunit complex, its macromolecular organization affects the dynamics of photosynthetic membranes. Here we reveal a chloroplast PSI from the green alga Chlamydomonas reinhardtii that is organized as a homodimer, comprising 40 protein subunits with 118 transmembrane helices that provide scaffold for 568 pigments. Cryogenic electron microscopy identified that the absence of PsaH and Lhca2 gives rise to a head-to-head relative orientation of the PSI-light-harvesting complex I monomers in a way that is essentially different from the oligomer formation in cyanobacteria. The light-harvesting protein Lhca9 is the key element for mediating this dimerization. The interface between the monomers is lacking PsaH and thus partially overlaps with the surface area that would bind one of the light-harvesting complex II complexes in state transitions. We also define the most accurate available PSI-light-harvesting complex I model at 2.3 Å resolution, including a flexibly bound electron donor plastocyanin, and assign correct identities and orientations to all the pigments, as well as 621 water molecules that affect energy transfer pathways.
Topics: Photosystem I Protein Complex; Plastocyanin; Light-Harvesting Protein Complexes; Protein Subunits; Cyanobacteria; Water; Photosystem II Protein Complex
PubMed: 36229605
DOI: 10.1038/s41477-022-01253-4 -
Frontiers in Plant Science 2022The photosynthetic electron transport chain is mineral rich. Specific mineral deficiencies can modify the electron transport chain specifically. Here, it is shown that...
Identification of Twelve Different Mineral Deficiencies in Hydroponically Grown Sunflower Plants on the Basis of Short Measurements of the Fluorescence and P700 Oxidation/Reduction Kinetics.
The photosynthetic electron transport chain is mineral rich. Specific mineral deficiencies can modify the electron transport chain specifically. Here, it is shown that on the basis of 2 short Chl fluorescence and P700 measurements (approx. 1 s each), it is possible to discriminate between 10 out of 12 different mineral deficiencies: B, Ca, Cu, Fe, K, Mg, Mn, Mo, N, P, S, and Zn. B- and Mo-deficient plants require somewhat longer measurements to detect the feedback inhibition they induce. Eight out of twelve deficiencies mainly affect PS I and NIR measurements are, therefore, very important for this analysis. In Cu- and P-deficient plants, electron flow from the plastoquinone pool to PS I, is affected. In the case of Cu-deficiency due to the loss of plastocyanin and in the case of P-deficiency probably due to a fast and strong generation of Photosynthetic Control. For several Ca-, K-, and Zn-deficient plant species, higher levels of reactive oxygen species have been measured in the literature. Here, it is shown that this not only leads to a loss of Pm (maximum P700 redox change) reflecting a lower PS I content, but also to much faster P700 re-reduction kinetics during the I-P (~30-200 ms) fluorescence rise phase. The different mineral deficiencies affect the relation between the I-P and P700 kinetics in different ways and this is used to discuss the nature of the relationship between these two parameters.
PubMed: 35720579
DOI: 10.3389/fpls.2022.894607 -
Proceedings of the National Academy of... Jan 2022Leaf senescence is a critical process in plants and has a direct impact on many important agronomic traits. Despite decades of research on senescence-altered mutants via...
Leaf senescence is a critical process in plants and has a direct impact on many important agronomic traits. Despite decades of research on senescence-altered mutants via forward genetics and functional assessment of senescence-associated genes (SAGs) via reverse genetics, the senescence signal and the molecular mechanism that perceives and transduces the signal remain elusive. Here, using dark-induced senescence (DIS) of leaf as the experimental system, we show that exogenous copper induces the senescence syndrome and transcriptomic changes in light-grown plants parallel to those in DIS. By profiling the transcriptomes and tracking the subcellular copper distribution, we found that reciprocal regulation of plastocyanin, the thylakoid lumen mobile electron carrier in the Z scheme of photosynthetic electron transport, and SAG14 and plantacyanin (PCY), a pair of interacting small blue copper proteins located on the endomembrane, is a common thread in different leaf senescence scenarios, including DIS. Genetic and molecular experiments confirmed that the PCY-SAG14 module is necessary and sufficient for promoting DIS. We also found that the PCY-SAG14 module is repressed by a conserved microRNA, miR408, which in turn is repressed by phytochrome interacting factor 3/4/5 (PIF3/4/5), the key trio of transcription factors promoting DIS. Together, these findings indicate that intracellular copper redistribution mediated by PCY-SAG14 has a regulatory role in DIS. Further deciphering the copper homeostasis mechanism and its interaction with other senescence-regulating pathways should provide insights into our understanding of the fundamental question of how plants age.
Topics: Arabidopsis; Arabidopsis Proteins; Copper; Darkness; Gene Expression Regulation, Plant; Light; MicroRNAs; Phytochrome; Plant Leaves; Plant Senescence; Plants, Genetically Modified; Transcription Factors; Transcriptome
PubMed: 35022242
DOI: 10.1073/pnas.2116623119 -
International Journal of Molecular... Jan 2022MicroRNA408 () is an ancient and highly conserved miRNA, which is involved in the regulation of plant growth, development and stress response. However, previous research... (Review)
Review
MicroRNA408 () is an ancient and highly conserved miRNA, which is involved in the regulation of plant growth, development and stress response. However, previous research results on the evolution and functional roles of and its targets are relatively scattered, and there is a lack of a systematic comparison and comprehensive summary of the detailed evolutionary pathways and regulatory mechanisms of and its targets in plants. Here, we analyzed the evolutionary pathway of in plants, and summarized the functions of and its targets in regulating plant growth and development and plant responses to various abiotic and biotic stresses. The evolutionary analysis shows that is an ancient and highly conserved microRNA, which is widely distributed in different plants. regulates the growth and development of different plants by down-regulating its targets, encoding blue copper (Cu) proteins, and by transporting Cu to plastocyanin (PC), which affects photosynthesis and ultimately promotes grain yield. In addition, improves tolerance to stress by down-regulating target genes and enhancing cellular antioxidants, thereby increasing the antioxidant capacity of plants. This review expands and promotes an in-depth understanding of the evolutionary and regulatory roles of and its targets in plants.
Topics: Biological Evolution; Gene Expression Regulation, Plant; MicroRNAs; Multigene Family; Organ Specificity; Plant Development; Plant Physiological Phenomena; RNA, Messenger; RNA, Plant; Stress, Physiological
PubMed: 35008962
DOI: 10.3390/ijms23010530 -
The ISME Journal May 2022Copper membrane monooxygenases (CuMMOs) play critical roles in the global carbon and nitrogen cycles. Organisms harboring these enzymes perform the first, and rate...
Copper membrane monooxygenases (CuMMOs) play critical roles in the global carbon and nitrogen cycles. Organisms harboring these enzymes perform the first, and rate limiting, step in aerobic oxidation of ammonia, methane, or other simple hydrocarbons. Within archaea, only organisms in the order Nitrososphaerales (Thaumarchaeota) encode CuMMOs, which function exclusively as ammonia monooxygenases. From grassland and hillslope soils and aquifer sediments, we identified 20 genomes from distinct archaeal species encoding divergent CuMMO sequences. These archaea are phylogenetically clustered in a previously unnamed Thermoplasmatota order, herein named the Ca. Angelarchaeales. The CuMMO proteins in Ca. Angelarchaeales are more similar in structure to those in Nitrososphaerales than those of bacteria, and contain all functional residues required for general monooxygenase activity. Ca. Angelarchaeales genomes are significantly enriched in blue copper proteins (BCPs) relative to sibling lineages, including plastocyanin-like electron carriers and divergent nitrite reductase-like (nirK) 2-domain cupredoxin proteins co-located with electron transport machinery. Ca. Angelarchaeales also encode significant capacity for peptide/amino acid uptake and degradation and share numerous electron transport mechanisms with the Nitrososphaerales. Ca. Angelarchaeales are detected at high relative abundance in some of the environments where their genomes originated from. While the exact substrate specificities of the novel CuMMOs identified here have yet to be determined, activity on ammonia is possible given their metabolic and ecological context. The identification of an archaeal CuMMO outside of the Nitrososphaerales significantly expands the known diversity of CuMMO enzymes in archaea and suggests previously unaccounted organisms contribute to critical global nitrogen and/or carbon cycling functions.
Topics: Ammonia; Archaea; Carbon; Copper; Euryarchaeota; Mixed Function Oxygenases; Phylogeny; Soil
PubMed: 34987183
DOI: 10.1038/s41396-021-01177-5 -
Small (Weinheim An Der Bergstrasse,... Feb 2022Charge separation and transport through the reaction center of photosystem I (PSI) is an essential part of the photosynthetic electron transport chain. A strategy is...
Charge separation and transport through the reaction center of photosystem I (PSI) is an essential part of the photosynthetic electron transport chain. A strategy is developed to immobilize and orient PSI complexes on gold electrodes allowing to probe the complex's electron acceptor side, the chlorophyll special pair P700. Electrochemical scanning tunneling microscopy (ECSTM) imaging and current-distance spectroscopy of single protein complex shows lateral size in agreement with its known dimensions, and a PSI apparent height that depends on the probe potential revealing a gating effect in protein conductance. In current-distance spectroscopy, it is observed that the distance-decay constant of the current between PSI and the ECSTM probe depends on the sample and probe electrode potentials. The longest charge exchange distance (lowest distance-decay constant β) is observed at sample potential 0 mV/SSC (SSC: reference electrode silver/silver chloride) and probe potential 400 mV/SSC. These potentials correspond to hole injection into an electronic state that is available in the absence of illumination. It is proposed that a pair of tryptophan residues located at the interface between P700 and the solution and known to support the hydrophobic recognition of the PSI redox partner plastocyanin, may have an additional role as hole exchange mediator in charge transport through PSI.
Topics: Chlorophyll; Electron Transport; Kinetics; Oxidation-Reduction; Photosynthesis; Photosystem I Protein Complex
PubMed: 34874621
DOI: 10.1002/smll.202104366 -
Plants (Basel, Switzerland) Jul 2021In the face of rising salinity along coastal regions and in irrigated areas, molecular breeding of tolerant crops and reforestation of exposed areas using tolerant woody...
In the face of rising salinity along coastal regions and in irrigated areas, molecular breeding of tolerant crops and reforestation of exposed areas using tolerant woody species is a two-way strategy. Thus, identification of tolerant plants and of existing tolerance mechanisms are of immense value. In the present study, three Eucalyptus ecotypes with potentially differential salt sensitivity were compared. Soil-grown Eucalyptus plants were exposed to 80 and 170 mM NaCl for 30 days. Besides analysing salt effects on ionic/osmotic balance, and hydrolytic enzymes, plants were compared for dynamics of light-induced redox changes in photosynthetic electron transport chain (pETC) components, namely plastocyanin (PC), photosystem I (PSI) and ferredoxin (Fd), parallel to traditional chlorophyll a fluorescence-based PSII-related parameters. Deconvoluted signals for PC and Fd from PSI allowed identification of PC and PSI as the prime salinity-sensitive components of pETC in tested Eucalyptus species. portrayed efficient K-Na balance (60-90% increased K) along with a more dynamic range of redox changes for pETC components in old leaves. Young leaves in showed robust endomembrane homeostasis, as underlined by an increased response of hydrolytic enzymes at lower salt concentration (~1.7-2.6-fold increase). Findings are discussed in context of salinity dose dependence among different Eucalyptus species.
PubMed: 34371604
DOI: 10.3390/plants10071401 -
Proceedings of the National Academy of... Jul 2021The Southern Ocean (SO) harbors some of the most intense phytoplankton blooms on Earth. Changes in temperature and iron availability are expected to alter the intensity...
The Southern Ocean (SO) harbors some of the most intense phytoplankton blooms on Earth. Changes in temperature and iron availability are expected to alter the intensity of SO phytoplankton blooms, but little is known about how these changes will influence community composition and downstream biogeochemical processes. We performed light-saturated experimental manipulations on surface ocean microbial communities from McMurdo Sound in the Ross Sea to examine the effects of increased iron availability (+2 nM) and warming (+3 and +6 °C) on nutrient uptake, as well as the growth and transcriptional responses of two dominant diatoms, and We found that community nutrient uptake and primary productivity were elevated under both warming conditions without iron addition (relative to ambient -0.5 °C). This effect was greater than additive under concurrent iron addition and warming. became more abundant under warming without added iron (especially at 6 °C), while only became more abundant under warming in the iron-added treatments. We attribute the apparent advantage shows under warming to up-regulation of iron-conserving photosynthetic processes, utilization of iron-economic nitrogen assimilation mechanisms, and increased iron uptake and storage. These data identify important molecular and physiological differences between dominant diatom groups and add to the growing body of evidence for 's increasingly important role in warming SO ecosystems. This study also suggests that temperature-driven shifts in SO phytoplankton assemblages may increase utilization of the vast pool of excess nutrients in iron-limited SO surface waters and thereby influence global nutrient distribution and carbon cycling.
Topics: Climate Change; Diatoms; Ecosystem; Eutrophication; Gene Expression Regulation; Light-Harvesting Protein Complexes; Nitrogen; Oceans and Seas; Photosynthesis; Phytoplankton; Plastocyanin
PubMed: 34301906
DOI: 10.1073/pnas.2107238118