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Nature Communications Nov 2023Cyclic electron transfer (CET) predominates when NADP is at basal levels, early in photosynthetic induction; however, the mechanism underlying the subsequent supply of...
Cyclic electron transfer (CET) predominates when NADP is at basal levels, early in photosynthetic induction; however, the mechanism underlying the subsequent supply of NADP to fully drive steady-state linear electron transfer remains unclear. Here, we investigated whether CET is involved in de novo NADP supply in Arabidopsis thaliana and measured chloroplastic NADP dynamics to evaluate responsiveness to variable light, photochemical inhibitors, darkness, and CET activity. The sum of oxidized and reduced forms shows that levels of NADP and NAD increase and decrease, respectively, in response to light; levels of NADP and NAD decrease and increase in the dark, respectively. Moreover, consistent with the pH change in the stroma, the pH preference of chloroplast NAD phosphorylation and NADP dephosphorylation is alkaline and weakly acidic, respectively. Furthermore, CET is correlated with upregulation of light-responsive NADP level increases and downregulation of dark-responsive NADP level reductions. These findings are consistent with CET helping to regulate NADP pool size via stromal pH regulation under fluctuating light conditions.
Topics: NADP; NAD; Chloroplasts; Electron Transport; Photosynthesis; Arabidopsis; Arabidopsis Proteins; Hydrogen-Ion Concentration; Oxidation-Reduction
PubMed: 37932304
DOI: 10.1038/s41467-023-42995-9 -
Journal of Bacteriology Oct 2023Cyanobacteria show an unusually complex prokaryotic cell structure including a distinct intracytoplasmic membrane system, the thylakoid membranes that are the site of...
Cyanobacteria show an unusually complex prokaryotic cell structure including a distinct intracytoplasmic membrane system, the thylakoid membranes that are the site of the photosynthetic light reactions. The thylakoid and plasma membranes have sharply distinct proteomes, but the mechanisms that target proteins to a specific membrane remain poorly understood. Here, we investigate the locations of translation of thylakoid and plasma membrane proteins in the model unicellular cyanobacterium PCC 7942. We use fluorescent hybridization to probe the locations of mRNAs encoding membrane-integral proteins, plus Green Fluorescent Protein tagging of the RplL subunit to reveal the location of ribosomes under different conditions. We show that membrane-integral thylakoid and plasma membrane proteins are translated in different locations. Thylakoid membrane proteins are translated in patches at the innermost thylakoid membrane surface facing the nucleoid. However, different proteins are translated in different patches, even when they are subunits of the same multiprotein complex. This implies that translation is distributed over the proximal thylakoid surface, with newly inserted proteins migrating within the membrane prior to incorporation into complexes. mRNAs encoding plasma membrane proteins form patches at the plasma membrane. Ribosomes can be observed at similar locations near the thylakoid and plasma membranes, with more ribosomes near the plasma membrane when conditions force rapid production of plasma membrane proteins. There must be routes for ribosomes and mRNAs past the thylakoids to the plasma membrane. We infer a system to chaperone plasma membrane mRNAs to prevent their translation prior to arrival at the correct membrane. IMPORTANCE Cyanobacteria have a complex and distinct membrane system within the cytoplasm, the thylakoid membranes that house the photosynthetic light reactions. The thylakoid and plasma membranes contain distinct sets of proteins, but the steps that target proteins to the two membranes remain unclear. Knowledge of the protein sorting rules will be crucial for the biotechnological re-engineering of cyanobacterial cells, and for understanding the evolutionary development of the thylakoids. Here, we probe the subcellular locations of the mRNAs that encode cyanobacterial membrane proteins and the ribosomes that translate them. We show that thylakoid and plasma membrane proteins are produced at different locations, providing the first direct evidence for a sorting mechanism that operates prior to protein translation.
Topics: Membrane Proteins; In Situ Hybridization, Fluorescence; Cyanobacteria; Thylakoids; Cell Membrane
PubMed: 37787518
DOI: 10.1128/jb.00209-23 -
Journal of Advanced Research Feb 2024In plants, gravity directs bidirectional growth; it specifies upward growth of shoots and downward growth of roots. Due to gravity, roots establish robust anchorage and... (Review)
Review
BACKGROUND
In plants, gravity directs bidirectional growth; it specifies upward growth of shoots and downward growth of roots. Due to gravity, roots establish robust anchorage and shoot, which enables to photosynthesize. It sets optimum posture and develops plant architecture to efficiently use resources like water, nutrients, CO, and gaseous exchange. Hence, gravitropism is crucial for crop productivity as well as for the growth of plants in challenging climate. Some SGR members are known to affect tiller and shoot angle, organ size, and inflorescence stem in plants.
AIM OF REVIEW
Although the SHOOT GRAVITROPISM (SGR) family plays a key role in regulating the fate of shoot gravitropism, little is known about its function compared to other proteins involved in gravity response in plant cells and tissues. Moreover, less information on the SGR family's physiological activities and biochemical responses in shoot gravitropism is available. This review scrutinizes and highlights the recent developments in shoot gravitropism and provides an outlook for future crop development, multi-application scenarios, and translational research to improve agricultural productivity.
KEY SCIENTIFIC CONCEPTS OF REVIEW
Plants have evolved multiple gene families specialized in gravitropic responses, of which the SGR family is highly significant. The SGR family regulates the plant's gravity response by regulating specific physiological and biochemical processes such as transcription, cell division, amyloplast sedimentation, endodermis development, and vacuole formation. Here, we analyze the latest discoveries in shoot gravitropism with particular attention to SGR proteins in plant cell biology, cellular physiology, and homeostasis. Plant cells detect gravity signals by sedimentation of amyloplast (starch granules) in the direction of gravity, and the signaling cascade begins. Gravity sensing, signaling, and auxin redistribution (organ curvature) are the three components of plant gravitropism. Eventually, we focus on the role of multiple SGR genes in shoot and present a complete update on the participation of SGR family members in gravity.
PubMed: 38295878
DOI: 10.1016/j.jare.2024.01.026 -
ELife Mar 2024The apicoplast is a four-membrane plastid found in the apicomplexans, which harbors biosynthesis and organelle housekeeping activities in the matrix. However, the...
The apicoplast is a four-membrane plastid found in the apicomplexans, which harbors biosynthesis and organelle housekeeping activities in the matrix. However, the mechanism driving the flux of metabolites, in and out, remains unknown. Here, we used TurboID and genome engineering to identify apicoplast transporters in . Among the many novel transporters, we show that one pair of apicomplexan monocarboxylate transporters (AMTs) appears to have evolved from a putative host cell that engulfed a red alga. Protein depletion showed that AMT1 and AMT2 are critical for parasite growth. Metabolite analyses supported the notion that AMT1 and AMT2 are associated with biosynthesis of isoprenoids and fatty acids. However, stronger phenotypic defects were observed for AMT2, including in the inability to establish parasite virulence in mice. This study clarifies, significantly, the mystery of apicoplast transporter composition and reveals the importance of the pair of AMTs in maintaining the apicoplast activity in apicomplexans.
Topics: Animals; Mice; Toxoplasma; Parasites; Apicoplasts; Fatty Acids; Organic Chemicals; Protozoan Proteins
PubMed: 38502570
DOI: 10.7554/eLife.88866 -
Nature Communications Dec 2023Phycobilisomes (PBS) are antenna megacomplexes that transfer energy to photosystems II and I in thylakoids. PBS likely evolved from a basic, inefficient form into the...
Phycobilisomes (PBS) are antenna megacomplexes that transfer energy to photosystems II and I in thylakoids. PBS likely evolved from a basic, inefficient form into the predominant hemidiscoidal shape with radiating peripheral rods. However, it has been challenging to test this hypothesis because ancestral species are generally inaccessible. Here we use spectroscopy and cryo-electron microscopy to reveal a structure of a "paddle-shaped" PBS from a thylakoid-free cyanobacterium that likely retains ancestral traits. This PBS lacks rods and specialized ApcD and ApcF subunits, indicating relict characteristics. Other features include linkers connecting two chains of five phycocyanin hexamers (CpcN) and two core subdomains (ApcH), resulting in a paddle-shaped configuration. Energy transfer calculations demonstrate that chains are less efficient than rods. These features may nevertheless have increased light absorption by elongating PBS before multilayered thylakoids with hemidiscoidal PBS evolved. Our results provide insights into the evolution and diversification of light-harvesting strategies before the origin of thylakoids.
Topics: Thylakoids; Phycobilisomes; Cryoelectron Microscopy; Photosystem I Protein Complex; Bacterial Proteins; Cyanobacteria
PubMed: 38049400
DOI: 10.1038/s41467-023-43646-9 -
Genomics May 2024Rubus, the largest genus in Rosaceae, contains over 1400 species that distributed in multiple habitats across the world, with high species diversity in the temperate... (Comparative Study)
Comparative Study
Rubus, the largest genus in Rosaceae, contains over 1400 species that distributed in multiple habitats across the world, with high species diversity in the temperate regions of Northern Hemisphere. Multiple Rubus species are cultivated for their valuable fruits. However, the intrageneric classification and phylogenetic relationships are still poorly understood. In this study, we sequenced, assembled, and characterized 17 plastomes of Rubus, and conducted comparative genomics integrating with 47 previously issued plastomes of this genus. The 64 plastomes of Rubus exhibited typical quadripartite structure with sizes ranging from 155,144 to 156,700 bp, and contained 132 genes including 87 protein-coding genes, 37 tRNA genes and eight rRNA genes. All plastomes are conservative in the gene order, the frequency of different types of long repeats and simple sequence repeats (SSRs), the codon usage, and the selection pressure of protein-coding genes. However, there are also some differences in the Rubus plastomes, including slight contraction and expansion of the IRs, a variation in the numbers of SSRs and long repeats, and some genes in certain clades undergoing intensified or relaxed purifying selection. Phylogenetic analysis based on whole plastomes showed that the monophyly of Rubus was strongly supported and resolved it into six clades corresponding to six subgenera. Moreover, we identified 12 highly variable regions that could be potential molecular markers for phylogenetic, population genetic, and barcoding studies. Overall, our study provided insight into plastomic structure and sequence diversification of Rubus, which could be beneficial for future studies on identification, evolution, and phylogeny in this genus.
Topics: Phylogeny; Rubus; Genomics; Genome, Chloroplast; Chloroplasts; Microsatellite Repeats; Evolution, Molecular; RNA, Transfer; Codon Usage
PubMed: 38614287
DOI: 10.1016/j.ygeno.2024.110845 -
Plant Physiology Aug 2023The visualization of photosynthesis-derived reactive oxygen species has been experimentally limited to pH-sensitive probes, unspecific redox dyes, and whole-plant...
The visualization of photosynthesis-derived reactive oxygen species has been experimentally limited to pH-sensitive probes, unspecific redox dyes, and whole-plant phenotyping. Recent emergence of probes that circumvent these limitations permits advanced experimental approaches to investigate in situ plastid redox properties. Despite growing evidence of heterogeneity in photosynthetic plastids, investigations have not addressed the potential for spatial variation in redox and/or reactive oxygen dynamics. To study the dynamics of H2O2 in distinct plastid types, we targeted the pH-insensitive, highly specific probe HyPer7 to the plastid stroma in Arabidopsis (Arabidopsis thaliana). Using HyPer7 and glutathione redox potential (EGSH) probe for redox-active green fluorescent protein 2 genetically fused to the redox enzyme human glutaredoxin-1 with live cell imaging and optical dissection of cell types, we report heterogeneities in H2O2 accumulation and redox buffering within distinct epidermal plastids in response to excess light and hormone application. Our observations suggest that plastid types can be differentiated by their physiological redox features. These data underscore the variation in photosynthetic plastid redox dynamics and demonstrate the need for cell-type-specific observations in future plastid phenotyping.
Topics: Humans; Hydrogen Peroxide; Plastids; Arabidopsis; Photosynthesis; Oxidation-Reduction
PubMed: 37226328
DOI: 10.1093/plphys/kiad307 -
Plant Signaling & Behavior Dec 2023The chloroplasts in terrestrial plants play a functional role as a major sensor for perceiving physiological changes under normal and stressful conditions. Despite the...
The chloroplasts in terrestrial plants play a functional role as a major sensor for perceiving physiological changes under normal and stressful conditions. Despite the fact that the plant chloroplast genome encodes around 120 genes, which are mainly essential for photosynthesis and chloroplast biogenesis, the functional roles of the genes remain to be determined in plant's response to environmental stresses. Photosynthetic electron transfer D (PETD) is a key component of the chloroplast cytochrome bf complex. Chloroplast ndhA (NADH dehydrogenase A) and ndhB (NADH dehydrogenase B) interact with photosystem I (PSI), forming NDH-PSI supercomplex. Notably, artificial targeting of chloroplasts-encoded proteins, PETD, NDHA, or NDHB, was successfully relocated from cytosols into chloroplasts. The result suggests that artificial targeting of proteins to chloroplasts is potentially open to the possibility of chloroplast biotechnology in engineering of plant tolerance against biotic and abiotic stresses.
Topics: Cytosol; Chloroplast Proteins; Cytochrome b6f Complex; NADH Dehydrogenase; Chloroplasts
PubMed: 37707988
DOI: 10.1080/15592324.2023.2258321 -
International Journal of Molecular... Apr 2024With the pronounced increase in nanotechnology, it is likely that biological systems will be exposed to excess nanoparticles (NPs). Cerium oxide nanoparticles (CeO NPs)... (Review)
Review
With the pronounced increase in nanotechnology, it is likely that biological systems will be exposed to excess nanoparticles (NPs). Cerium oxide nanoparticles (CeO NPs) are among the most abundantly produced nanomaterials in the world. Their widespread use raises fundamental questions related to the accumulation in the environment and further interactions with living organisms, especially plants. NPs present in either soil or soilless environments are absorbed by the plant root systems and further transported to the aboveground parts. After entering the cytoplasm, NPs interact with chloroplast, nucleus, and other structures responsible for metabolic processes at the cellular level. In recent years, several studies have shown the impact of nanoceria on plant growth and metabolic processes. Research performed on different plants has shown a dual role for CeO NPs. The observed effects can be positive or negative and strongly depend on the plant species, characterization, and concentrations of NPs. This review describes the impact of root-applied CeO NPs on plant growth, photosynthesis, metal homeostasis, and parameters of induced oxidative stress.
Topics: Nanoparticles; Nanostructures; Biological Transport; Chloroplasts; Cerium
PubMed: 38612829
DOI: 10.3390/ijms25074018 -
Plants (Basel, Switzerland) Nov 2023Isoprenoids are a wide family of metabolites including high-value chemicals, flavors, pigments, and drugs. Isoprenoids are particularly abundant and diverse in plants....
Isoprenoids are a wide family of metabolites including high-value chemicals, flavors, pigments, and drugs. Isoprenoids are particularly abundant and diverse in plants. The methyl-D-erythritol 4-phosphate (MEP) pathway produces the universal isoprenoid precursors isopentenyl diphosphate and dimethylallyl diphosphate in plant plastids for the downstream production of monoterpenes, diterpenes, and photosynthesis-related isoprenoids such as carotenoids, chlorophylls, tocopherols, phylloquinone, and plastoquinone. The enzyme deoxy-D-xylulose 5-phosphate synthase (DXS) is the first and main rate-determining enzyme of the MEP pathway. In tomato (), a plant with an active isoprenoid metabolism in several tissues, three genes encode DXS-like proteins (SlDXS1 to 3). Here, we show that the expression patterns of the three genes suggest distinct physiological roles without excluding that they might function together in some tissues. We also confirm that SlDXS1 and 2 are true DXS enzymes, whereas SlDXS3 lacks DXS activity. We further show that SlDXS1 and 2 co-localize in plastidial speckles and that they can be immunoprecipitated together, suggesting that they might form heterodimers in vivo in at least some tissues. These results provide novel insights for the biotechnological use of DXS isoforms in metabolic engineering strategies to up-regulate the MEP pathway flux.
PubMed: 38005784
DOI: 10.3390/plants12223886