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1.
Mol Biol Evol ; 40(1)2023 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-36625177

RESUMO

Recent advances in long-read sequencing technology have allowed for single-molecule sequencing of entire mitochondrial genomes, opening the door for direct investigation of the mitochondrial genome architecture and recombination. We used PacBio sequencing to reassemble mitochondrial genomes from two species of New Zealand freshwater snails, Potamopyrgus antipodarum and Potamopyrgus estuarinus. These assemblies revealed a ∼1.7 kb structure within the mitochondrial genomes of both species that was previously undetected by an assembly of short reads and likely corresponding to a large noncoding region commonly present in the mitochondrial genomes. The overall architecture of these Potamopyrgus mitochondrial genomes is reminiscent of the chloroplast genomes of land plants, harboring a large single-copy (LSC) region and a small single-copy (SSC) region separated by a pair of inverted repeats (IRa and IRb). Individual sequencing reads that spanned across the Potamopyrgus IRa-SSC-IRb structure revealed the occurrence of a "flip-flop" recombination. We also detected evidence for two distinct IR haplotypes and recombination between them in wild-caught P. estuarinus, as well as extensive intermolecular recombination between single-nucleotide polymorphisms in the LSC region. The chloroplast-like architecture and repeat-mediated mitochondrial recombination we describe here raise fundamental questions regarding the origins and commonness of inverted repeats in cytoplasmic genomes and their role in mitochondrial genome evolution.


Assuntos
Genoma de Cloroplastos , Genoma Mitocondrial , Animais , Análise de Sequência de DNA , Recombinação Genética , Cloroplastos , Filogenia
2.
Nat Plants ; 9(1): 68-80, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36646831

RESUMO

The genomes of cytoplasmic organelles (mitochondria and plastids) are maternally inherited in most eukaryotes, thus excluding organellar genomes from the benefits of sexual reproduction and recombination. The mechanisms underlying maternal inheritance are largely unknown. Here we demonstrate that two independently acting mechanisms ensure maternal inheritance of the plastid (chloroplast) genome. Conducting large-scale genetic screens for paternal plastid transmission, we discovered that mild chilling stress during male gametogenesis leads to increased entry of paternal plastids into sperm cells and strongly increased paternal plastid transmission. We further show that the inheritance of paternal plastid genomes is controlled by the activity of a genome-degrading exonuclease during pollen maturation. Our data reveal that (1) maternal inheritance breaks down under specific environmental conditions, (2) an organelle exclusion mechanism and a genome degradation mechanism act in concert to prevent paternal transmission of plastid genes and (3) plastid inheritance is determined by complex gene-environment interactions.


Assuntos
Pólen , Sementes , Pólen/genética , Plastídeos/genética , Mitocôndrias/genética , Cloroplastos
3.
Sci Rep ; 13(1): 1356, 2023 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-36693990

RESUMO

Sphaeropteris lepifera is a tree fern in the Cyatheaceae, a family that has played an important role in the evolution of plant systems. This study aimed to analyze the complete chloroplast genome of S. lepifera and compared it with previously published chloroplast genomes Cyatheaceae family. The chloroplast genome of S. lepifera comprised 162,114 bp, consisting of a large single copy (LSC) region of 86,327 bp, a small single copy (SSC) region of 27,731 bp and a pair of inverted repeats (IRa and IRb) of 24,028 bp each. The chloroplast genome encoded 129 genes, comprising 32 transfer RNAs, 8 ribosomal RNAs, and 89 protein-coding genes. Comparison of the genomes of 7 Cyatheaceae plants showed that the chloroplast genome of S. lepifera was missing the gene trnV-UAC. Expansion of the SSC region led to the difference in the chloroplast genome size of S. lepifera. Eight genes, atpI, ccsA, petA, psaB, rpl16, rpoA, rpoC1, and ycf2 have high nucleic acid diversity and can be regarded as potential molecular markers. The genes trnG-trnR and atpB were suitable for DNA barcodes between different communities of S. lepifera. The S. lepifera groups in Zhejiang Province probably diffused from Pingtan and Ningde, Fujian. The results will provide a basis for species identification, biological studies, and endangerment mechanism of S. lepifera.


Assuntos
Gleiquênias , Genoma de Cloroplastos , Gleiquênias/genética , Filogenia , Estrutura Molecular , Cloroplastos/genética
4.
Proc Natl Acad Sci U S A ; 120(5): e2215575120, 2023 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-36696445

RESUMO

Chloroplast division involves the coordination of protein complexes from the stroma to the cytosol. The Min system of chloroplasts includes multiple stromal proteins that regulate the positioning of the division site. The outer envelope protein PLASTID DIVISION1 (PDV1) was previously reported to recruit the cytosolic chloroplast division protein ACCUMULATION AND REPLICATION OF CHLOROPLAST5 (ARC5). However, we show here that PDV1 is also important for the stability of the inner envelope chloroplast division protein PARALOG OF ARC6 (PARC6), a component of the Min system. We solved the structure of both the C-terminal domain of PARC6 and its complex with the C terminus of PDV1. The formation of an intramolecular disulfide bond within PARC6 under oxidized conditions prevents its interaction with PDV1. Interestingly, this disulfide bond can be reduced by light in planta, thus promoting PDV1-PARC6 interaction and chloroplast division. Interaction with PDV1 can induce the dimerization of PARC6, which is important for chloroplast division. Magnesium ions, whose concentration in chloroplasts increases upon light exposure, also promote the PARC6 dimerization. This study highlights the multilayer regulation of the PDV1-PARC6 interaction as well as chloroplast division.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Plastídeos/metabolismo , Cloroplastos/metabolismo , Dissulfetos/metabolismo , Dinaminas/metabolismo
5.
Sci Rep ; 13(1): 896, 2023 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-36650197

RESUMO

Chloroplasts have evolved from photosynthetic cyanobacteria-like progenitors through endosymbiosis. The chloroplasts of present-day land plants have their own transcription and translation systems that show several similarities with prokaryotic organisms. A remarkable feature of the chloroplast translation system is the use of non-AUG start codons in the protein synthesis of certain genes that are evolutionarily conserved from Algae to angiosperms. However, the biological significance of such use of non-AUG codons is not fully understood. The present study was undertaken to unravel the significance of non-AUG start codons in vivo using the chloroplast genetic engineering approach. For this purpose, stable transplastomic tobacco plants expressing a reporter gene i.e. uidA (GUS) under four different start codons (AUG/UUG/GUG/CUG) were generated and ß-glucuronidase (GUS) expression was compared. To investigate further the role of promoter sequences proximal to the start codon, uidA was expressed under two different chloroplast gene promoters psbA and psbC that use AUG and a non-AUG (GUG) start codons, respectively, and also showed significant differences in the DNA sequence surrounding the start codon. Further, to delineate the role of RNA editing that creates AUG start codon by editing non-AUG codons, if any, which is another important feature of the chloroplast transcription and translation system, transcripts were sequenced. In addition, a proteomic approach was used to identify the translation initiation site(s) of GUS and the N-terminal amino acid encoded when expressed under different non-AUG start codons. The results showed that chloroplasts use non-AUG start codons in combination with the translation initiation site as an additional layer of gene regulation to over-express proteins that are required at high levels due to their high rates of turnover.


Assuntos
Biossíntese de Proteínas , Proteômica , Códon de Iniciação/genética , Biossíntese de Proteínas/genética , Códon/genética , Cloroplastos/genética , Iniciação Traducional da Cadeia Peptídica/genética
6.
Int J Mol Sci ; 24(2)2023 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-36674866

RESUMO

Heat stress severely affects plant growth and crop production. It is therefore urgent to uncover the mechanisms underlying heat stress responses of plants and establish the strategies to enhance heat tolerance of crops. The chloroplasts and mitochondria are known to be highly sensitive to heat stress. Heat stress negatively impacts on the electron transport chains, leading to increased production of reactive oxygen species (ROS) that can cause damages on the chloroplasts and mitochondria. Disruptions of photosynthetic and respiratory metabolisms under heat stress also trigger increase in ROS and alterations in redox status in the chloroplasts and mitochondria. However, ROS and altered redox status in these organelles also activate important mechanisms that maintain functions of these organelles under heat stress, which include HSP-dependent pathways, ROS scavenging systems and retrograde signaling. To discuss heat responses associated with energy regulating organelles, we should not neglect the energy regulatory hub involving TARGET OF RAPAMYCIN (TOR) and SNF-RELATED PROTEIN KINASE 1 (SnRK1). Although roles of TOR and SnRK1 in the regulation of heat responses are still unknown, contributions of these proteins to the regulation of the functions of energy producing organelles implicate the possible involvement of this energy regulatory hub in heat acclimation of plants.


Assuntos
Cloroplastos , Mitocôndrias , Espécies Reativas de Oxigênio/metabolismo , Cloroplastos/metabolismo , Oxirredução , Mitocôndrias/metabolismo , Resposta ao Choque Térmico , Produtos Agrícolas/metabolismo
7.
Plant Signal Behav ; 18(1): 2163345, 2023 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-36592637

RESUMO

Plantago asiatica L. is a representative individual species of Plantaginaceae, whose high reputation is owed to its edible and medicinal values. However, the phylogeny and genes of the P. asiatica chloroplast have not yet been well described. Here we report the findings of a comprehensive analysis of the P. asiatica chloroplast genome. The P. asiatica chloroplast genome is 164,992 bp, circular, and has a GC content of 37.98%. The circular genome contains 141 genes, including 8 rRNAs, 38 tRNAs, and 95 protein-coding genes. Seventy-two simple sequence repeats are detected. Comparative chloroplast genome analysis of six related species suggests that a higher similarity exists in the coding region than the non-coding region, and differences in the degree of preservation is smaller between P. asiatica and Plantago depressa than among others. Our phylogenetic analysis illustrates P. asiatica has a relatively close relationship with P. depressa, which was also divided into different clades with Plantago ovata and Plantago lagopus in the genus Plantago. This analysis of the P. asiatica chloroplast genome contributes to an improved deeply understanding of the evolutionary relationships among Plantaginaceae.


Assuntos
Genoma de Cloroplastos , Plantaginaceae , Plantago , Plantago/genética , Plantaginaceae/genética , Filogenia , Genoma de Cloroplastos/genética , Cloroplastos/genética
8.
RNA ; 29(2): 141-152, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36649983

RESUMO

The adaptiveness of nonsynonymous RNA editing (recoding) could be conferred by the flexibility of the temporal-spatially controllable proteomic diversity, or by its restorative effect which fixes unfavorable genomic mutations at the RNA level. These two complementary hypotheses, namely, the diversifying hypothesis and the restorative hypothesis, have distinct predictions on the landscape of RNA editing sites. We collected the chloroplast C-to-U RNA editomes of 21 vascular plants (11 angiosperms, four gymnosperms, and six ferns) from a previous study, aiming to testify whether the plant editomes typically conform to the restorative hypothesis. All predictions made by the restorative hypothesis are verified: (i) nonsynonymous editing sites are more frequent and have higher editing levels than synonymous sites; (ii) nonsynonymous editing levels are extremely high and show weak tissue-specificity in plants; (iii) on the inferred genomic sites with recent T-to-C mutations, nonsynonymous sites but not synonymous sites are compensated by C-to-U RNA editing. In conclusion, nonsynonymous C-to-U RNA editing in plants is adaptive due to its restorative effects. The recoding levels are high and are constantly required across the whole plant so that the recoding events could perfectly mimic DNA mutations. The evolutionary significance of plant RNA editing is systematically demonstrated at the genome-wide level.


Assuntos
Edição de RNA , RNA de Cloroplastos , RNA de Cloroplastos/genética , Edição de RNA/genética , Proteômica , RNA de Plantas/genética , Cloroplastos/genética , Cloroplastos/metabolismo , Plantas/genética , Plantas/metabolismo
9.
BMC Plant Biol ; 23(1): 15, 2023 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-36611140

RESUMO

BACKGROUND: Soybean is an important protein- and oil-rich crop throughout the world. Much attention has been paid to its nuclear genome, which is bi-parentally inherited and associated with many important agronomical traits. However, less is known about the genomes of the semi-autonomous and essential organelles, chloroplasts and mitochondria, of soybean. RESULTS: Here, through analyzing the polymorphisms of these organelles in 2580 soybean accessions including 107 wild soybeans, we found that the chloroplast genome is more variable than the mitochondrial genome in terms of variant density. Consistent with this, more haplotypes were found in the chloroplast genome (44 haplotypes) than the mitochondrial genome (30 haplotypes). These haplotypes were distributed extremely unevenly with the top two haplotypes (CT1 and CT2 for chloroplasts, MT1 and MT2 for mitochondria) accounting for nearly 70 and 18% of cultivated soybean accessions. Wild soybeans also exhibited more diversity in organelle genomes, harboring 32 chloroplast haplotypes and 19 mitochondrial haplotypes. However, only a small percentage of cultivated soybeans shared cytoplasm with wild soybeans. In particular, the two most frequent types of cytoplasm (CT1/MT1, CT2/MT2) were missing in wild soybeans, indicating that wild soybean cytoplasm has been poorly exploited during breeding. Consistent with the hypothesis that soybean originated in China, we found that China harbors the highest cytoplasmic diversity in the world. The geographical distributions of CT1-CT3 and MT1-MT3 in Northeast China were not significantly different from those in Middle and South China. Two mitochondrial polymorphism sites, p.457333 (T > C) and p.457550 (G > A), were found to be heterozygous in most soybeans, and heterozygosity appeared to be associated with the domestication of cultivated soybeans from wild soybeans, the improvement of landraces to generate elite cultivated soybeans, and the geographic adaptation of soybean. CONCLUSIONS: The haplotypes of thousands of soybean cultivars should be helpful in evaluating the impact of cytoplasm on soybean performance and in breeding cultivars with the desired cytoplasm. Mitochondrial heterozygosity might be related to soybean adaptation, and this hypothesis needs to be further investigated.


Assuntos
Genoma Mitocondrial , Soja , Soja/genética , Genoma Mitocondrial/genética , Melhoramento Vegetal , Haplótipos/genética , Cloroplastos/genética , Polimorfismo de Nucleotídeo Único , Variação Genética
10.
BMC Biotechnol ; 23(1): 1, 2023 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-36611158

RESUMO

BACKGROUND: Chloroplast transformation is a robust technology for the expression of recombinant proteins. Various types of pharmaceutical proteins including growth factors have been reported in chloroplasts via chloroplast transformation approach at high expression levels. However, high expression of epidermal growth factor (EGF) in chloroplasts with the technology is still unavailable. RESULTS: The present work explored the high-level expression of recombinant EGF, a protein widely applied in many clinical therapies, in tobacco chloroplasts. In this work, homoplastic transgenic plants expressing fusion protein GFP-EGF, which was composed of GFP and EGF via a linker, were generated. The expression of GFP-EGF was confirmed by the combination of green fluorescent observation and Western blotting. The achieved accumulation of the recombinant fusion GFP-EGF was 10.21 ± 0.27% of total soluble proteins (1.57 ± 0.05 g kg- 1 of fresh leaf). The chloroplast-derived GFP-EGF was capable of increasing the cell viability of the NSLC cell line A549 and enhancing the phosphorylation level of the EGF receptor in the A549 cells. CONCLUSION: The expression of recombinant EGF in tobacco chloroplasts via chloroplast transformation method was achieved at considerable accumulation level. The attempt gives a good example for the application of chloroplast transformation technology in recombinant pharmaceutical protein production.


Assuntos
Fator de Crescimento Epidérmico , Tabaco , Humanos , Fator de Crescimento Epidérmico/genética , Fator de Crescimento Epidérmico/metabolismo , Tabaco/genética , Tabaco/metabolismo , Cloroplastos/genética , Cloroplastos/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Proteínas Recombinantes/metabolismo , Preparações Farmacêuticas/metabolismo
11.
Proc Natl Acad Sci U S A ; 120(3): e2216497120, 2023 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-36638210

RESUMO

Plants have developed intricate mechanisms to adapt to changing light conditions. Besides phototropism and heliotropism (differential growth toward light and diurnal motion with respect to sunlight, respectively), chloroplast motion acts as a fast mechanism to change the intracellular structure of leaf cells. While chloroplasts move toward the sides of the plant cell to avoid strong light, they accumulate and spread out into a layer on the bottom of the cell at low light to increase the light absorption efficiency. Although the motion of chloroplasts has been studied for over a century, the collective organelle motion leading to light-adapting self-organized structures remains elusive. Here, we study the active motion of chloroplasts under dim-light conditions, leading to an accumulation in a densely packed quasi-2D layer. We observe burst-like rearrangements and show that these dynamics resemble systems close to the glass transition by tracking individual chloroplasts. Furthermore, we provide a minimal mathematical model to uncover relevant system parameters controlling the stability of the dense configuration of chloroplasts. Our study suggests that the meta-stable caging close to the glass transition in the chloroplast monolayer serves a physiological relevance: Chloroplasts remain in a spread-out configuration to increase the light uptake but can easily fluidize when the activity is increased to efficiently rearrange the structure toward an avoidance state. Our research opens questions about the role that dynamical phase transitions could play in self-organized intracellular responses of plant cells toward environmental cues.


Assuntos
Cloroplastos , Células Vegetais , Cloroplastos/fisiologia , Luz Solar , Fototropismo , Folhas de Planta/fisiologia , Luz
12.
Sci Rep ; 13(1): 760, 2023 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-36641535

RESUMO

The chloroplast genome of 5959 species was analyzed to construct the anticodon table of the chloroplast genome. Analysis of the chloroplast transfer ribonucleic acid (tRNA) revealed the presence of a putative quadruplet anticodon containing tRNAs in the chloroplast genome. The tRNAs with putative quadruplet anticodons were UAUG, UGGG, AUAA, GCUA, and GUUA, where the GUUA anticodon putatively encoded tRNAAsn. The study also revealed the complete absence of tRNA genes containing ACU, CUG, GCG, CUC, CCC, and CGG anticodons in the chloroplast genome from the species studied so far. The chloroplast genome was also found to encode tRNAs encoding N-formylmethionine (fMet), Ile2, selenocysteine, and pyrrolysine. The chloroplast genomes of mycoparasitic and heterotrophic plants have had heavy losses of tRNA genes. Furthermore, the chloroplast genome was also found to encode putative spacer tRNA, tRNA fragments (tRFs), tRNA-derived, stress-induced RNA (tiRNAs), and the group I introns. An evolutionary analysis revealed that chloroplast tRNAs had evolved via multiple common ancestors and the GC% had more influence toward encoding the tRNA number in the chloroplast genome than the genome size.


Assuntos
Anticódon , Genoma de Cloroplastos , Anticódon/genética , Sequência de Bases , RNA de Transferência/genética , Cloroplastos/genética
13.
Plant Commun ; 4(1): 100509, 2023 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-36560880

RESUMO

The cytochrome b6f (Cyt b6f) complex is a multisubunit protein complex in chloroplast thylakoid membranes required for photosynthetic electron transport. Here we report the isolation and characterization of the new tiny albino 1 (nta1) mutant in Arabidopsis, which has severe defects in Cyt b6f accumulation and chloroplast development. Gene cloning revealed that the nta1 phenotype was caused by disruption of a single nuclear gene, NTA1, which encodes an integral thylakoid membrane protein conserved across green algae and plants. Overexpression of NTA1 completely rescued the nta1 phenotype, and knockout of NTA1 in wild-type plants recapitulated the mutant phenotype. Loss of NTA1 function severely impaired the accumulation of multiprotein complexes related to photosynthesis in thylakoid membranes, particularly the components of Cyt b6f. NTA1 was shown to directly interact with four subunits (Cyt b6/PetB, PetD, PetG, and PetN) of Cyt b6f through the DUF1279 domain and C-terminal sequence to mediate their assembly. Taken together, our results identify NTA1 as a new and key regulator of chloroplast development that plays essential roles in assembly of the Cyt b6f complex by interacting with multiple Cyt b6f subunits.


Assuntos
Arabidopsis , Complexo Citocromos b6f , Arabidopsis/genética , Arabidopsis/metabolismo , Cloroplastos/metabolismo , Complexo Citocromos b6f/genética , Complexo Citocromos b6f/metabolismo , Citocromos b/metabolismo , Proteínas de Membrana/metabolismo , Plantas/metabolismo , Tilacoides/metabolismo , Proteínas de Arabidopsis/metabolismo
14.
J Plant Physiol ; 280: 153894, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36525836

RESUMO

Mahonia bealei and Mahonia fortunei are important plant resources in Traditional Chinese Medicine that are valued for their high levels of benzylisoquinoline alkaloids (BIAs). Although the phytotoxic activity of BIAs has been recognized, information is limited on the mechanism of action by which these compounds regulate photosynthetic activity. Here, we performed comparative chloroplast genome analysis to examine insertions and deletions in the two species. We found a GATA-motif located in the promoter region of the ndhF gene of only M. bealei. K-mer frequency-based diversity analysis illustrated the close correlation between the GATA-motif and leaf phenotype. We found that the GATA-motif significantly inhibits GUS gene expression in tobacco during the dark-light transition (DLT). The expression of ndhF was downregulated in M. bealei and upregulated in M. fortunei during the DLT. NDH-F activity was remarkably decreased and exhibited a significant negative correlation with BIA levels in M. bealei during the DLT. Furthermore, the NADPH produced through photosynthetic metabolism was found to decrease in M. bealei during the DLT. Taken together, our results indicate that this GATA-motif might act as the functional site by which BIAs inhibit photosynthetic metabolism through downregulating ndhF expression during the DLT.


Assuntos
Alcaloides , Benzilisoquinolinas , Mahonia , Mahonia/química , Extratos Vegetais/farmacologia , Cloroplastos
15.
J Photochem Photobiol B ; 238: 112622, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36527964

RESUMO

Due to the misuse of various antibiotics, the problem of bacterial resistance has become more serious worldwide, and the associated diseases have significantly increased the medical burden of society. Antimicrobial photodynamic therapy (PDT) has received widespread attention because of its safety, efficiency, and facile implementation. Here, we report an oxygen-supply antibacterial agent (Ce6@CS/CP), which could enhance the efficacy of antibacterial PDT via photosynthesis of O2. Ce6@CS/CP displayed a robust interaction with bacteria, hence facilitating the delivery efficiency of Ce6. In vitro experiments demonstrated that the photodynamic bactericidal potency of Ce6@CS/CP was remarkably greater than that of free Ce6. Furthermore, Ce6@CS/CP also exhibited superior significant antibiofilm activity to free Ce6. As a live oxygen-supply antibacterial agent, Ce6@CS/CP possesses excellent bacteria delivery ability of Ce6 and could enhance the potency of antibacterial PDT by photosynthesis, offering a new strategy for fighting against drug-resistant bacteria.


Assuntos
Clorofilídeos , Fotoquimioterapia , Porfirinas , Preparações Farmacêuticas , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Bactérias , Cloroplastos , Biofilmes , Oxigênio , Fármacos Fotossensibilizantes/farmacologia , Fármacos Fotossensibilizantes/uso terapêutico
16.
J Photochem Photobiol B ; 238: 112623, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36549082

RESUMO

Foraminifera are unicellular, marine organisms that occur worldwide. A very common species in the German Wadden Sea is Elphidium williamsoni. Some foraminifera (such as elphidia) are able to use kleptoplastidy, which allows them to incorporate chloroplasts from their algal food source into their own cell body. The experiments reported here are based on the fact that chlorophyll (a and c) can be detected in the intact cells with spectroscopic methods in the visible spectral range, which allows an indirect investigation of the presence of sequestered chloroplasts. Starving experiments of E. williamsoni in the light (24 h continuous) showed that the greatest decrease in chlorophyll content was recorded within the first 20-30 days. From day 60 on, chlorophyll was hardly detectable. Through subsequent feeding on a renewed algal food source a significant increase in the chlorophyll content in foraminifera was noticed. The degradation of chlorophyll in the dark (24 h continuous darkness) during the starving period was much more complex. Chlorophyll was still detected in the cells after 113 days of starving time. Therefore, we hypotheses that the effect of photoinhibition applies to chloroplasts in foraminifera under continuous illumination.


Assuntos
Foraminíferos , Foraminíferos/metabolismo , Cloroplastos/metabolismo , Clorofila/metabolismo , Luz
17.
Mol Plant ; 16(1): 187-205, 2023 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-36540023

RESUMO

During photosynthesis, light energy is utilized to drive sophisticated biochemical chains of electron transfers, converting solar energy into chemical energy that feeds most life on earth. Cyclic electron transfer/flow (CET/CEF) plays an essential role in efficient photosynthesis, as it balances the ATP/NADPH ratio required in various regulatory and metabolic pathways. Photosystem I, cytochrome b6f, and NADH dehydrogenase (NDH) are large multisubunit protein complexes embedded in the thylakoid membrane of the chloroplast and key players in NDH-dependent CEF pathway. Furthermore, small mobile electron carriers serve as shuttles for electrons between these membrane protein complexes. Efficient electron transfer requires transient interactions between these electron donors and acceptors. Structural biology has been a powerful tool to advance our knowledge of this important biological process. A number of structures of the membrane-embedded complexes, soluble electron carrier proteins, and transient complexes composed of both have now been determined. These structural data reveal detailed interacting patterns of these electron donor-acceptor pairs, thus allowing us to visualize the different parts of the electron transfer process. This review summarizes the current state of structural knowledge of three membrane complexes and their interaction patterns with mobile electron carrier proteins.


Assuntos
Fotossíntese , Complexo de Proteína do Fotossistema I , Transporte de Elétrons , Complexo de Proteína do Fotossistema I/metabolismo , Tilacoides/metabolismo , Cloroplastos/metabolismo
18.
J Plant Physiol ; 280: 153899, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36566670

RESUMO

The photorespiratory repair pathway (photorespiration in short) was set up from ancient metabolic modules about three billion years ago in cyanobacteria, the later ancestors of chloroplasts. These prokaryotes developed the capacity for oxygenic photosynthesis, i.e. the use of water as a source of electrons and protons (with O2 as a by-product) for the sunlight-driven synthesis of ATP and NADPH for CO2 fixation in the Calvin cycle. However, the CO2-binding enzyme, ribulose 1,5-bisphosphate carboxylase (known under the acronym Rubisco), is not absolutely selective for CO2 and can also use O2 in a side reaction. It then produces 2-phosphoglycolate (2PG), the accumulation of which would inhibit and potentially stop the Calvin cycle and subsequently photosynthetic electron transport. Photorespiration removes the 2-PG and in this way prevents oxygenic photosynthesis from poisoning itself. In plants, the core of photorespiration consists of ten enzymes distributed over three different types of organelles, requiring interorganellar transport and interaction with several auxiliary enzymes. It goes together with the release and to some extent loss of freshly fixed CO2. This disadvantageous feature can be suppressed by CO2-concentrating mechanisms, such as those that evolved in C4 plants thirty million years ago, which enhance CO2 fixation and reduce 2PG synthesis. Photorespiration itself provided a pioneer variant of such mechanisms in the predecessors of C4 plants, C3-C4 intermediate plants. This article is a review and update particularly on the enzyme components of plant photorespiration and their catalytic mechanisms, on the interaction of photorespiration with other metabolism and on its impact on the evolution of photosynthesis. This focus was chosen because a better knowledge of the enzymes involved and how they are embedded in overall plant metabolism can facilitate the targeted use of the now highly advanced methods of metabolic network modelling and flux analysis. Understanding photorespiration more than before as a process that enables, rather than reduces, plant photosynthesis, will help develop rational strategies for crop improvement.


Assuntos
Dióxido de Carbono , Ribulose-Bifosfato Carboxilase , Ribulose-Bifosfato Carboxilase/metabolismo , Dióxido de Carbono/metabolismo , Fotossíntese , Plantas/metabolismo , Cloroplastos/metabolismo , Oxigênio/metabolismo
19.
BMC Plant Biol ; 22(1): 570, 2022 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-36471240

RESUMO

BACKGROUND: Leaf color mutants are ideal materials to study pigment metabolism and photosynthesis. Leaf color variations are mainly affected by chlorophylls (Chls) and carotenoid contents and chloroplast development in higher plants. However, the regulation of chlorophyll metabolism remains poorly understood in many plant species. The chloroplast signal-recognition particle system is responsible for the insertion of the light-harvesting chlorophyll a/b proteins (LHCPs) to thylakoid membranes, which controls the chloroplast development as well as the regulation of Chls biosynthesis post-translationally in higher plants. RESULTS: In this study, the yellow leaf cucumber mutant, named yl, was found in an EMS-induced mutant library, which exhibited a significantly reduced chlorophyll content, abnormal chloroplast ultrastructure and decreased photosynthetic capacity. Genetic analysis demonstrated that the phenotype of yl was controlled by a recessive nuclear gene. Using BSA-seq technology combined with the map-based cloning method, we narrowed the locus to a 100 kb interval in chromosome 3. Linkage analysis and allelism test validated the candidate SNP residing in CsaV3_3G009150 encoding one homolog of chloroplast signal-recognition particle (cpSRP) receptor in Arabidopsis, cpFtsY, could be responsible for the yellow leaf phenotype of yl. The relative expression of CscpFtsY was significantly down-regulated in different organs except for the stem, of yl compared with that in the wild type (WT). Subcellular localization result showed that CscpFtsY located in the chloroplasts of mesophyll cells. CONCLUSIONS: The yl mutant displayed Chls-deficient, impaired chloroplast ultrastructure with intermittent grana stacks and significantly decreased photosynthetic capacity. The isolation of CscpFtsY in cucumber could accelerate the progress on chloroplast development by cpSRP-dependant LHCP delivery system and regulation of Chls biosynthesis in a post-translational way.


Assuntos
Arabidopsis , Cucumis sativus , Cucumis sativus/genética , Cucumis sativus/metabolismo , Clorofila A/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Folhas de Planta/metabolismo , Cloroplastos/metabolismo , Fenótipo , Clorofila/metabolismo , Arabidopsis/genética , Complexos de Proteínas Captadores de Luz/genética , Partícula de Reconhecimento de Sinal/metabolismo , Regulação da Expressão Gênica de Plantas , Mutação
20.
BMC Genomics ; 23(1): 794, 2022 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-36460956

RESUMO

BACKGROUND: Dicranostigma leptopodum (Maxim.) Fedde is a perennial herb with bright yellow flowers, well known as "Hongmao Cao" for its medicinal properties, and is an excellent early spring flower used in urban greening. However, its molecular genomic information remains largely unknown. Here, we sequenced and analyzed the chloroplast genome of D. leptopodum to discover its genome structure, organization, and phylogenomic position within the subfamily Papaveroideae. RESULTS: The chloroplast genome size of D. leptopodum was 162,942 bp, and D. leptopodum exhibited a characteristic circular quadripartite structure, with a large single-copy (LSC) region (87,565 bp), a small single-copy (SSC) region (18,759 bp) and a pair of inverted repeat (IR) regions (28,309 bp). The D. leptopodum chloroplast genome encoded 113 genes, including 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. The dynamics of the genome structures, genes, IR contraction and expansion, long repeats, and single sequence repeats exhibited similarities, with slight differences observed among the eight Papaveroideae species. In addition, seven interspace regions and three coding genes displayed highly variable divergence, signifying their potential to serve as molecular markers for phylogenetic and species identification studies. Molecular evolution analyses indicated that most of the genes were undergoing purifying selection. Phylogenetic analyses revealed that D. leptopodum formed a clade with the tribe Chelidonieae. CONCLUSIONS: Our study provides detailed information on the D. leptopodum chloroplast genome, expanding the available genomic resources that may be used for future evolution and genetic diversity studies.


Assuntos
Genoma de Cloroplastos , Filogenia , Cloroplastos/genética , Genômica , Evolução Molecular
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