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The ISME Journal Jun 2024As unicellular predators, ciliates engage in close associations with diverse microbes, laying the foundation for the establishment of endosymbiosis. Originally...
As unicellular predators, ciliates engage in close associations with diverse microbes, laying the foundation for the establishment of endosymbiosis. Originally heterotrophic, ciliates demonstrate the ability to acquire phototrophy by phagocytizing unicellular algae or by sequestering algal plastids. This adaptation enables them to gain photosynthate and develop resistance to unfavorable environmental conditions. The integration of acquired phototrophy with intrinsic phagotrophy results in a trophic mode known as mixotrophy. Additionally, ciliates can harbor thousands of bacteria in various intracellular regions, including the cytoplasm and nucleus, exhibiting species specificity. Under prolonged and specific selective pressure within hosts, bacterial endosymbionts evolve unique lifestyles and undergo particular reductions in metabolic activities. Investigating the research advancements in various endosymbiotic cases within ciliates will contribute to elucidate patterns in cellular interaction and unravel the evolutionary origins of complex traits.
PubMed: 38916437
DOI: 10.1093/ismejo/wrae117 -
Functional & Integrative Genomics Jun 2024Chloroplasts are not only critical photosynthesis sites in plants, but they also participate in plastidial retrograde signaling in response to developmental and...
Chloroplasts are not only critical photosynthesis sites in plants, but they also participate in plastidial retrograde signaling in response to developmental and environmental signals. MEcPP (2-C-Methyl-D-erythritol-2,4-cyclopyrophosphate) is an intermediary in the methylerythritol phosphate (MEP) pathway in chloroplasts. It is a critical precursor for the synthesis of isoprenoids and terpenoid derivatives, which play crucial roles in plant growth and development, photosynthesis, reproduction, and defense against environmental constraints. Accumulation of MEcPP under stressful conditions triggers the expression of IMPα-9 and TPR2, contributing to the activation of abiotic stress-responsive genes. In this correspondence, we discuss plastidial retrograde signaling in support of a recently published paper in Molecular Plant (Zeng et al. 2024). We hope that it can shed more insight on the retrograde signaling cascade.
Topics: Chloroplasts; Stress, Physiological; Gene Expression Regulation, Plant; Signal Transduction; Arabidopsis; Erythritol; Arabidopsis Proteins; Sugar Phosphates; MAP Kinase Kinase Kinase 5
PubMed: 38910225
DOI: 10.1007/s10142-024-01395-y -
Communications Biology Jun 2024Although the chloroplast genome (cpDNA) of higher plants is known to exist as a large protein-DNA complex called 'plastid nucleoid', researches on its DNA state and...
Although the chloroplast genome (cpDNA) of higher plants is known to exist as a large protein-DNA complex called 'plastid nucleoid', researches on its DNA state and regulatory elements are limited. In this study, we performed the assay for transposase-accessible chromatin sequencing (ATAC-seq) on five common tissues across five grasses, and found that the accessibility of different regions in cpDNA varied widely, with the transcribed regions being highly accessible and accessibility patterns around gene start and end sites varying depending on the level of gene expression. Further analysis identified a total of 3970 putative protein binding footprints on cpDNAs of five grasses. These footprints were enriched in intergenic regions and co-localized with known functional elements. Footprints and their flanking accessibility varied dynamically among tissues. Cross-species analysis showed that footprints in coding regions tended to overlap non-degenerate sites and contain a high proportion of highly conserved sites, indicating that they are subject to evolutionary constraints. Taken together, our results suggest that the accessibility of cpDNA has biological implications and provide new insights into the transcriptional regulation of chloroplasts.
Topics: Genome, Chloroplast; Poaceae; DNA, Chloroplast; Gene Expression Regulation, Plant; Chloroplasts
PubMed: 38909165
DOI: 10.1038/s42003-024-06374-4 -
Nature Communications Jun 2024The methylerythritol phosphate (MEP) pathway is responsible for biosynthesis of the precursors of isoprenoid compounds in eubacteria and plastids. It is a metabolic... (Review)
Review
The methylerythritol phosphate (MEP) pathway is responsible for biosynthesis of the precursors of isoprenoid compounds in eubacteria and plastids. It is a metabolic alternative to the well-known mevalonate pathway for isoprenoid production found in archaea and eukaryotes. Recently, a role for the MEP pathway in oxidative stress detection, signalling, and response has been identified. This role is executed in part through the unusual cyclic intermediate, methylerythritol cyclodiphosphate (MEcDP). We postulate that this response is triggered through the oxygen sensitivity of the MEP pathway's terminal iron-sulfur (Fe-S) cluster enzymes. MEcDP is the substrate of IspG, the first Fe-S cluster enzyme in the pathway; it accumulates under oxidative stress conditions and acts as a signalling molecule. It may also act as an antioxidant. Furthermore, evidence is emerging for a broader and highly nuanced role of the MEP pathway in oxidative stress responses, implemented through a complex system of differential regulation and sensitivity at numerous nodes in the pathway. Here, we explore the evidence for such a role (including the contribution of the Fe-S cluster enzymes and different pathway metabolites, especially MEcDP), the evolutionary implications, and the many questions remaining about the behaviour of the MEP pathway in the presence of oxidative stress.
Topics: Oxidative Stress; Erythritol; Sugar Phosphates; Iron-Sulfur Proteins; Signal Transduction; Terpenes
PubMed: 38906898
DOI: 10.1038/s41467-024-49483-8 -
Proceedings of the National Academy of... Jun 2024Hydrogen isotope ratios (δH) represent an important natural tracer of metabolic processes, but quantitative models of processes controlling H-fractionation in aquatic...
Hydrogen isotope ratios (δH) represent an important natural tracer of metabolic processes, but quantitative models of processes controlling H-fractionation in aquatic photosynthetic organisms are lacking. Here, we elucidate the underlying physiological controls of H/H fractionation in algal lipids by systematically manipulating temperature, light, and CO(aq) in continuous cultures of the haptophyte . We analyze the hydrogen isotope fractionation in alkenones (α), a class of acyl lipids specific to this species and other haptophyte algae. We find a strong decrease in the α with increasing CO(aq) and confirm α correlates with temperature and light. Based on the known biosynthesis pathways, we develop a cellular model of the δH of algal acyl lipids to evaluate processes contributing to these controls on fractionation. Simulations show that longer residence times of NADPH in the chloroplast favor a greater exchange of NADPH with H-richer intracellular water, increasing α. Higher chloroplast CO(aq) and temperature shorten NADPH residence time by enhancing the carbon fixation and lipid synthesis rates. The inverse correlation of α to CO(aq) in our cultures suggests that carbon concentrating mechanisms (CCM) do not achieve a constant saturation of CO at the Rubisco site, but rather that chloroplast CO varies with external CO(aq). The pervasive inverse correlation of α with CO(aq) in the modern and preindustrial ocean also suggests that natural populations may not attain a constant saturation of Rubisco with the CCM. Rather than reconstructing growth water, α may be a powerful tool to elucidate the carbon limitation of photosynthesis.
Topics: Carbon Dioxide; Haptophyta; Lipids; Photosynthesis; Hydrogen; Chloroplasts; Deuterium; NADP; Temperature; Chemical Fractionation; Lipid Metabolism
PubMed: 38905238
DOI: 10.1073/pnas.2318570121 -
Science Advances Jun 2024Chloroplasts are the powerhouse of the plant cell, and their activity must be matched to plant growth to avoid photooxidative damage. We have identified a...
Chloroplasts are the powerhouse of the plant cell, and their activity must be matched to plant growth to avoid photooxidative damage. We have identified a posttranslational mechanism linking the eukaryotic target of rapamycin (TOR) kinase that promotes growth and the guanosine tetraphosphate (ppGpp) signaling pathway of prokaryotic origins that regulates chloroplast activity and photosynthesis in particular. We find that RelA SpoT homolog 3 (RSH3), a nuclear-encoded enzyme responsible for ppGpp biosynthesis, interacts directly with the TOR complex via a plant-specific amino-terminal region which is phosphorylated in a TOR-dependent manner. Down-regulating TOR activity causes a rapid increase in ppGpp synthesis in RSH3 overexpressors and reduces photosynthetic capacity in an RSH-dependent manner in wild-type plants. The TOR-RSH3 signaling axis therefore regulates the equilibrium between chloroplast activity and plant growth, setting a precedent for the regulation of organellar function by TOR.
Topics: Photosynthesis; Chloroplasts; Arabidopsis Proteins; Signal Transduction; Arabidopsis; Phosphorylation; Protein Processing, Post-Translational; Gene Expression Regulation, Plant; Guanosine Tetraphosphate; TOR Serine-Threonine Kinases; Phosphatidylinositol 3-Kinases
PubMed: 38896607
DOI: 10.1126/sciadv.adj3268 -
Physiologia Plantarum 2024Electron flow through the electron transport chain (ETC) is essential for oxidative phosphorylation in mitochondria and photosynthesis in chloroplasts. Electron fluxes... (Review)
Review
Electron flow through the electron transport chain (ETC) is essential for oxidative phosphorylation in mitochondria and photosynthesis in chloroplasts. Electron fluxes depend on environmental parameters, e.g., ionic and osmotic conditions and endogenous factors, and this may cause severe imbalances. Plants have evolved alternative sinks to balance the reductive load on the electron transport chains in order to avoid overreduction, generation of reactive oxygen species (ROS), and to cope with environmental stresses. These sinks act primarily as valves for electron drainage and secondarily as regulators of tolerance-related metabolism, utilizing the excess reductive energy. High salinity is an environmental stressor that stimulates the generation of ROS and oxidative stress, which affects growth and development by disrupting the redox homeostasis of plants. While glycophytic plants are sensitive to high salinity, halophytic plants tolerate, grow, and reproduce at high salinity. Various studies have examined the ETC systems of glycophytic plants, however, information about the state and regulation of ETCs in halophytes under non-saline and saline conditions is scarce. This review focuses on alternative electron sinks in chloroplasts and mitochondria of halophytic plants. In cases where information on halophytes is lacking, we examined the available knowledge on the relationship between alternative sinks and gradual salinity resilience of glycophytes. To this end, transcriptional responses of involved components of photosynthetic and respiratory ETCs were compared between the glycophyte Arabidopsis thaliana and the halophyte Schrenkiella parvula, and the time-courses of these transcripts were examined in A. thaliana. The observed regulatory patterns are discussed in the context of reactive molecular species formation in halophytes and glycophytes.
Topics: Chloroplasts; Salt-Tolerant Plants; Mitochondria; Reactive Oxygen Species; Salinity; Electron Transport; Photosynthesis
PubMed: 38894507
DOI: 10.1111/ppl.14397 -
International Journal of Molecular... May 2024Photosystem II (PSII) functions were investigated in basil ( L.) plants sprayed with 1 mM salicylic acid (SA) under non-stress (NS) or mild drought-stress (MiDS)...
Photosystem II (PSII) functions were investigated in basil ( L.) plants sprayed with 1 mM salicylic acid (SA) under non-stress (NS) or mild drought-stress (MiDS) conditions. Under MiDS, SA-sprayed leaves retained significantly higher (+36%) chlorophyll content compared to NS, SA-sprayed leaves. PSII efficiency in SA-sprayed leaves under NS conditions, evaluated at both low light (LL, 200 μmol photons m s) and high light (HL, 900 μmol photons m s), increased significantly with a parallel significant decrease in the excitation pressure at PSII (1-) and the excess excitation energy (EXC). This enhancement of PSII efficiency under NS conditions was induced by the mechanism of non-photochemical quenching (NPQ) that reduced singlet oxygen (O) production, as indicated by the reduced quantum yield of non-regulated energy loss in PSII (Φ). Under MiDS, the thylakoid structure of water-sprayed leaves appeared slightly dilated, and the efficiency of PSII declined, compared to NS conditions. In contrast, the thylakoid structure of SA-sprayed leaves did not change under MiDS, while PSII functionality was retained, similar to NS plants at HL. This was due to the photoprotective heat dissipation by NPQ, which was sufficient to retain the same percentage of open PSII reaction centers (q), as in NS conditions and HL. We suggest that the redox status of the plastoquinone pool (q) under MiDS and HL initiated the acclimation response to MiDS in SA-sprayed leaves, which retained the same electron transport rate (ETR) with control plants. Foliar spray of SA could be considered as a method to improve PSII efficiency in basil plants under NS conditions, at both LL and HL, while under MiDS and HL conditions, basil plants could retain PSII efficiency similar to control plants.
Topics: Photosystem II Protein Complex; Salicylic Acid; Ocimum basilicum; Droughts; Plant Leaves; Stress, Physiological; Chlorophyll; Photosynthesis; Thylakoids; Light
PubMed: 38891916
DOI: 10.3390/ijms25115728 -
Cells May 2024Through the shikimate pathway, a massive metabolic flux connects the central carbon metabolism with the synthesis of chorismate, the common precursor of the aromatic...
Through the shikimate pathway, a massive metabolic flux connects the central carbon metabolism with the synthesis of chorismate, the common precursor of the aromatic amino acids phenylalanine, tyrosine, and tryptophan, as well as other compounds, including salicylate or folate. The alternative metabolic channeling of chorismate involves a key branch-point, finely regulated by aromatic amino acid levels. Chorismate mutase catalyzes the conversion of chorismate to prephenate, a precursor of phenylalanine and tyrosine and thus a vast repertoire of fundamental derived compounds, such as flavonoids or lignin. The regulation of this enzyme has been addressed in several plant species, but no study has included conifers or other gymnosperms, despite the importance of the phenolic metabolism for these plants in processes such as lignification and wood formation. Here, we show that maritime pine ( Aiton) has two genes that encode for chorismate mutase, and . Our investigations reveal that these genes encode plastidial isoenzymes displaying activities enhanced by tryptophan and repressed by phenylalanine and tyrosine. Using phylogenetic studies, we have provided new insights into the possible evolutionary origin of the cytosolic chorismate mutases in angiosperms involved in the synthesis of phenylalanine outside the plastid. Studies based on different platforms of gene expression and co-expression analysis have allowed us to propose that PpCM2 plays a central role in the phenylalanine synthesis pathway associated with lignification.
Topics: Chorismate Mutase; Pinus; Phylogeny; Plant Proteins; Gene Expression Regulation, Plant; Phenylalanine; Plastids; Tryptophan
PubMed: 38891061
DOI: 10.3390/cells13110929 -
Cells May 2024Improving the drought resistance of rice is of great significance for expanding the planting area and improving the stable yield of rice. In our previous work, we found...
Improving the drought resistance of rice is of great significance for expanding the planting area and improving the stable yield of rice. In our previous work, we found that () protein promoted enhanced tolerance to drought stress by eliminating reactive oxygen species (ROS) levels and triggering the abscisic acid (ABA) response. However, the mechanism through which REL1 regulates drought tolerance by removing ROS is unclear. In this study, we identified REL1 interacting protein 5 (RIP5) and found that it directly combines with REL1 in the chloroplast. We found that was strongly expressed in ZH11 under drought-stress conditions, and that the mutants significantly improved the tolerance of rice plants to drought, whereas overexpression of resulted in greater susceptibility to drought. Further investigation suggested that negatively regulated drought tolerance in rice by decreasing the content of ascorbic acid (AsA), thereby reducing ROS clearance. RNA sequencing showed that the knockout of caused differential gene expression that is chiefly associated with ascorbate and aldarate metabolism. Furthermore, multiple experimental results suggest that is involved in regulating drought tolerance by inhibiting . Collectively, our findings reveal the importance of the inhibition of RIP5 by REL1 in affecting the rice's response to drought stress. This work not only explains the drought tolerance mechanism of rice, but will also help to improve the drought tolerance of rice.
Topics: Oryza; Plant Proteins; Droughts; Gene Expression Regulation, Plant; Reactive Oxygen Species; Stress, Physiological; Abscisic Acid; Chloroplasts; Adaptation, Physiological; Plants, Genetically Modified; Ascorbic Acid; Protein Binding; Drought Resistance
PubMed: 38891020
DOI: 10.3390/cells13110887