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Scientific Reports Jun 2024The twin-arginine translocation (Tat) system transports folded proteins across energized biological membranes in bacteria, plastids, and plant mitochondria. In...
The twin-arginine translocation (Tat) system transports folded proteins across energized biological membranes in bacteria, plastids, and plant mitochondria. In Escherichia coli, the three membrane proteins TatA, TatB and TatC associate to enable Tat transport. While TatB and TatC together form complexes that bind Tat-dependently transported proteins, the TatA component is responsible for the permeabilization of the membrane during transport. With wild type Tat systems, the TatB- and TatC-containing Tat complexes TC1 and TC2 can be differentiated. Their TatA content has not been resolved, nor could they be assigned to any step of the translocation mechanism. It is therefore a key question of current Tat research to understand how TatA associates with Tat systems during transport. By analyzing affinity-purified Tat complexes with mutations in TatC that selectively enrich either TC1 or TC2, we now for the first time demonstrate that both Tat complexes associate with TatA, but the larger TC2 recruits significantly more TatA than the smaller TC1. Most TatA co-purified as multimeric clusters. Using site-specific photo cross-linking, we could detect TatA-TatC interactions only near TatC transmembrane helices 5 and 6. Substrate-binding did not change the interacting positions but affected the stability of the interaction, pointing to a substrate-induced conformational transition. Together, our findings indicate that TatA clusters associate with TatBC without being integrated into the complex by major rearrangements. The increased TatA affinity of the larger Tat complex TC2 suggests that functional assembly is advanced in this complex.
Topics: Escherichia coli Proteins; Escherichia coli; Membrane Transport Proteins; Cell Membrane; Protein Transport; Protein Folding; Protein Binding; Mutation
PubMed: 38877109
DOI: 10.1038/s41598-024-64547-x -
Ecotoxicology and Environmental Safety Jul 2024Selenium (Se), as a vital stress ameliorant, possesses a beneficial effect on mediating detrimental effects of environmental threats. However, the mechanisms of Se in...
Selenium (Se), as a vital stress ameliorant, possesses a beneficial effect on mediating detrimental effects of environmental threats. However, the mechanisms of Se in mitigating the deleterious effects of drought are still poorly understood. Gentiana macrophylla Pall. is a well-known Chinese medicinal herb, and its root, as the main medicinal site, has significant therapeutic effects. The purpose of this experiment was to investigate the functions of Se on the seedling growth and physiobiochemical characteristics in G. macrophylla subjected to drought stress. The changes in microstructure and chloroplast ultrastructure of G. macrophylla leaves under drought exposure were characterized by scanning electron microscopy (SEM), scanning electron microscopes and energy dispersive X-Ray spectroscope (SEM-EDX), and transmission electron microscopy (TEM), respectively. Results revealed that drought stress induced a notable increase in oxidative toxicity in G. macrophylla, as evidenced by elevated levels of hydrogen peroxide (HO), lipid peroxidation (MDA), enhanced antioxidative response, decreased plant photosynthetic function, and inhibited plant growth. Chloroplasts integrity with damaged membranes and excess osmiophilic granule were observed in the drought-stressed plants. Se supplementation notably recovered the stomatal morphology, anatomical structure damage, and chloroplast ultrastructure of G. macrophylla leaves caused by drought exposure. Exogenous Se application markedly enhanced SPAD, photosynthetic stomatal exchange parameters, and photosystem II activity. Se supplementation significantly promoted the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), while reducing levels of MDA, superoxide anion (O) and HO, and improving membrane integrity. Furthermore, the ameliorative effects of Se were also suggested by increased contents of osmotic substances (soluble sugar and proline), boosted content of gentiopicroside and loganinic acid in roots, and alleviated the inhibition in plant growth and biomass. Fourier transform infrared (FTIR) analysis of Se-treated G. macrophylla roots under drought stress demonstrated that Se-stimulated metabolites including O-H, C-H, N-H, C-N, and CO functional groups, were involved in resisting drought stress. Correlation analysis indicated an obvious negative correlation between growth parameters and MDA, O and HO content, while a positive correlation with photosynthetic gas exchange parameters. Principal component analysis (PCA) results explained the total variance into two principal components contributing the maximum (93.50 %) among the drought exposure with or without Se due to the various experiment indexes. In conclusion, Se exerts beneficial properties on drought-induced detrimental effects in G. macrophylla by relieving oxidative stress, improving photosynthesis indexes, PSII activity, regulating anatomical changes, altering levels of gentiopicroside and loganinic acid, and promoting growth of drought-stressed G. macrophylla.
Topics: Gentiana; Selenium; Droughts; Plant Leaves; Photosynthesis; Stress, Physiological; Chloroplasts; Lipid Peroxidation; Hydrogen Peroxide; Oxidative Stress; Seedlings; Antioxidants; Plant Roots
PubMed: 38875819
DOI: 10.1016/j.ecoenv.2024.116591 -
Scientific Reports Jun 2024Neltuma alba (Algarrobo blanco), Neltuma chilensis (Algarrobo Chileno) and Strombocarpa strombulifera (Fortuna) are some of the few drought resistant trees and shrubs...
Neltuma alba (Algarrobo blanco), Neltuma chilensis (Algarrobo Chileno) and Strombocarpa strombulifera (Fortuna) are some of the few drought resistant trees and shrubs found in small highly fragmented populations, throughout the Atacama Desert. We reconstructed their plastid genomes using de novo assembly of paired-end reads from total genomic DNA. We found that the complete plastid genomes of N. alba and N. chilensis are larger in size compared to species of the Strombocarpa genus. The Strombocarpa species presented slightly more GC content than the Neltuma species. Therefore, we assume that Strombocarpa species have been exposed to stronger natural selection than Neltuma species. We observed high variation values in the number of cpSSRs (chloroplast simple sequence repeats) and repeated elements among Neltuma and Strombocarpa species. The p-distance results showed a low evolutionary divergence within the genus Neltuma, whereas a high evolutionary divergence was observed between Strombocarpa species. The molecular divergence time found in Neltuma and Strombocarpa show that these genera diverged in the late Oligocene. With this study we provide valuable information about tree species that provide important ecosystem services in hostile environments which can be used to determine these species in the geographically isolated communities, and keep the highly fragmented populations genetically healthy.
Topics: Phylogeny; Evolution, Molecular; Desert Climate; Genome, Plastid; Genetic Variation; Base Composition
PubMed: 38871769
DOI: 10.1038/s41598-024-64287-y -
Wellcome Open Research 2024We present the genome assembly of the pennate diatom strain UHM3201 (Ochrophyta; Bacillariophyceae; Rhopalodiales; Rhopalodiaceae) and that of its cyanobacterial...
We present the genome assembly of the pennate diatom strain UHM3201 (Ochrophyta; Bacillariophyceae; Rhopalodiales; Rhopalodiaceae) and that of its cyanobacterial endosymbiont (Chroococcales: Aphanothecaceae). The genome sequence of the diatom is 60.3 megabases in span, and the cyanobacterial genome has a length of 2.48 megabases. Most of the diatom nuclear genome assembly is scaffolded into 15 chromosomal pseudomolecules. The organelle genomes have also been assembled, with the mitochondrial genome 40.08 kilobases and the plastid genome 130.75 kilobases in length. A number of other prokaryote MAGs were also assembled.
PubMed: 38867757
DOI: 10.12688/wellcomeopenres.21534.1 -
Nature Communications Jun 2024Cryptophytes are ancestral photosynthetic organisms evolved from red algae through secondary endosymbiosis. They have developed alloxanthin-chlorophyll a/c2-binding...
Cryptophytes are ancestral photosynthetic organisms evolved from red algae through secondary endosymbiosis. They have developed alloxanthin-chlorophyll a/c2-binding proteins (ACPs) as light-harvesting complexes (LHCs). The distinctive properties of cryptophytes contribute to efficient oxygenic photosynthesis and underscore the evolutionary relationships of red-lineage plastids. Here we present the cryo-electron microscopy structure of the Photosystem II (PSII)-ACPII supercomplex from the cryptophyte Chroomonas placoidea. The structure includes a PSII dimer and twelve ACPII monomers forming four linear trimers. These trimers structurally resemble red algae LHCs and cryptophyte ACPI trimers that associate with Photosystem I (PSI), suggesting their close evolutionary links. We also determine a Chl a-binding subunit, Psb-γ, essential for stabilizing PSII-ACPII association. Furthermore, computational calculation provides insights into the excitation energy transfer pathways. Our study lays a solid structural foundation for understanding the light-energy capture and transfer in cryptophyte PSII-ACPII, evolutionary variations in PSII-LHCII, and the origin of red-lineage LHCIIs.
Topics: Photosystem II Protein Complex; Light-Harvesting Protein Complexes; Cryptophyta; Cryoelectron Microscopy; Photosynthesis; Models, Molecular; Energy Transfer; Photosystem I Protein Complex; Chlorophyll A
PubMed: 38866834
DOI: 10.1038/s41467-024-49453-0 -
Plant Physiology and Biochemistry : PPB Jun 2024In land plants plastid type differentiation occurs concomitantly with cellular differentiation and the transition from one type to another is under developmental and...
In land plants plastid type differentiation occurs concomitantly with cellular differentiation and the transition from one type to another is under developmental and environmental control. Plastid dynamism is based on a bilateral communication between plastids and nucleus through anterograde and retrograde signaling. Signaling occurs through the interaction with specific phytohormones (abscisic acid, strigolactones, jasmonates, gibberellins, brassinosteroids, ethylene, salicylic acid, cytokinin and auxin). The review is focused on the modulation of plastid capabilities at both transcriptional and post-translational levels at the crossroad between development and stress, with a particular attention to the chloroplast, because the most studied plastid type. The role of plastid-encoded and nuclear-encoded proteins for plastid development and stress responses, and the changes of plastid fate through the activity of stromules and plastoglobules, are discussed. Examples of plastid dynamism in response to soil stress agents (salinity, lead, cadmium, arsenic, and chromium) are described. Albinism and root greening are described based on the modulation activities of auxin and cytokinin. The physiological and functional responses of the sensory epidermal and vascular plastids to abiotic and biotic stresses along with their specific roles in stress sensing are described together with their potential modulation of retrograde signaling pathways. Future research perspectives include an in-depth study of sensory plastids to explore their potential for establishing a transgenerational memory to stress. Suggestions about anterograde and retrograde pathways acting at interspecific level and on the lipids of plastoglobules as a novel class of plastid morphogenic agents are provided.
PubMed: 38861821
DOI: 10.1016/j.plaphy.2024.108813 -
Plant Molecular Biology Jun 2024Mitochondria and plastids, originated as ancestral endosymbiotic bacteria, contain their own DNA sequences. These organelle DNAs (orgDNAs) are, despite the limited...
Mitochondria and plastids, originated as ancestral endosymbiotic bacteria, contain their own DNA sequences. These organelle DNAs (orgDNAs) are, despite the limited genetic information they contain, an indispensable part of the genetic systems but exist as multiple copies, making up a substantial amount of total cellular DNA. Given this abundance, orgDNA is known to undergo tissue-specific degradation in plants. Previous studies have shown that the exonuclease DPD1, conserved among seed plants, degrades orgDNAs during pollen maturation and leaf senescence in Arabidopsis. However, tissue-specific orgDNA degradation was shown to differ among species. To extend our knowledge, we characterized DPD1 in rice in this study. We created a genome-edited (GE) mutant in which OsDPD1 and OsDPD1-like were inactivated. Characterization of this GE plant demonstrated that DPD1 was involved in pollen orgDNA degradation, whereas it had no significant effect on orgDNA degradation during leaf senescence. Comparison of transcriptomes from wild-type and GE plants with different phosphate supply levels indicated that orgDNA had little impact on the phosphate starvation response, but instead had a global impact in plant growth. In fact, the GE plant showed lower fitness with reduced grain filling rate and grain weight in natural light conditions. Taken together, the presented data reinforce the important physiological roles of orgDNA degradation mediated by DPD1.
Topics: Oryza; Plant Proteins; Exonucleases; Gene Editing; Gene Expression Regulation, Plant; DNA, Plant; Pollen; Plant Leaves; Genome, Plant; Mutation
PubMed: 38856917
DOI: 10.1007/s11103-024-01452-x -
Wellcome Open Research 2023We present a genome assembly from a specimen of (the silverweed cinquefoil; Streptophyta; eudicotyledons; Rosales; Potentilleae). The haploid genome sequence is 237...
We present a genome assembly from a specimen of (the silverweed cinquefoil; Streptophyta; eudicotyledons; Rosales; Potentilleae). The haploid genome sequence is 237 megabases in span. Most of the assembly is scaffolded into seven chromosomal pseudomolecules. The mitochondrial and plastid genomes have also been assembled and are 294.6 and 155.6 kilobases in length respectively.
PubMed: 38855725
DOI: 10.12688/wellcomeopenres.19908.1 -
Frontiers in Plant Science 2024The orchid genus comprises three species, all discovered in the 21 century. Each of these species is achlorophyllous, mycoheterotrophic and is known to be endemic to...
The orchid genus comprises three species, all discovered in the 21 century. Each of these species is achlorophyllous, mycoheterotrophic and is known to be endemic to Vietnam. The type species of the genus, , occurs in a single location in northern Vietnam within a lowland limestone karstic area. and , in contrast, are confined to mountains of southern Vietnam, far away from any limestone formations. Taxonomic placement of remained uncertain for the reason of inconclusive morphological affinities. At the same time, the genus has never been included into molecular phylogenetic studies. We investigate the phylogenetic relationships of two species of ( and ) based on three DNA datasets: (1) a dataset comprising two nuclear regions, (2) a dataset comprising two plastid regions, and (3) a dataset employing data on the entire plastid genomes. Our phylogenetic reconstructions support the placement of into the subtribe Orchidinae (tribe Orchideae, subfamily Orchidoideae). This leads to a conclusion that the previously highlighted similarities in the rhizome morphology between and certain mycoheterotrophic genera of the subfamilies Epidendroideae and Vanilloideae are examples of a convergence. is deeply nested within Orchidinae, and therefore the subtribe Vietorchidinae is to be treated as a synonym of Orchidinae. In the obtained phylogenetic reconstructions, is sister to the photosynthetic genus . is restricted to limestone mountains, which allows to speculate that association with limestone karst is plesiomorphic for . Flower morphology is concordant with the molecular data in placing into Orchidinae and strongly supports the assignment of the genus to one of the two major clades within this subtribe. Within this clade, however, shows no close structural similarity with any of its genera; in particular, the proximity between and has never been proposed. Finally, we assembled the plastid genome of , which is 65969 bp long and contains 45 unique genes, being one of the most reduced plastomes in the subfamily Orchidoideae. The plastome of lacks any rearrangements in comparison with the closest studied autotrophic species, and possesses substantially contracted inverted repeats. No signs of positive selection acting on the protein-coding plastid sequences were detected.
PubMed: 38855461
DOI: 10.3389/fpls.2024.1393225 -
Frontiers in Plant Science 2023The hyperdiverse orchid genus is the second largest genus of flowering plants and exhibits a pantropical distribution with a center of diversity in tropical Asia. The...
The hyperdiverse orchid genus is the second largest genus of flowering plants and exhibits a pantropical distribution with a center of diversity in tropical Asia. The only section with a center of diversity in Australasia is sect. . However, the phylogenetic placement, interspecific relationships, and spatio-temporal evolution of this section remain largely unclear. To infer broad-level relationships within , and interspecific relationships within sect. , a genome skimming dataset was generated for 89 samples, which yielded 70 plastid coding regions and a nuclear ribosomal DNA cistron. For 18 additional samples, Sanger data from two plastid loci (K and 1) and nuclear ITS were added using a supermatrix approach. The study provided new insights into broad-level relationships in , including phylogenetic evidence for the non-monophyly of sections , , , , , , , , , and . Section and sect. formed a highly supported clade that was resolved as a sister group to the remainder of the genus. Divergence time estimations based on a relaxed molecular clock model placed the origin of in the Early Oligocene (ca. 33.2 Ma) and sect. in the Late Oligocene (ca. 23.6 Ma). Ancestral range estimations based on a BAYAREALIKE model identified the Australian continent as the ancestral area of the sect. The section underwent crown diversification from the mid-Miocene to the late Pleistocene, predominantly in continental Australia. At least two independent long-distance dispersal events were inferred eastward from the Australian continent to New Zealand and to New Caledonia from the early Pliocene onwards, likely mediated by predominantly westerly winds of the Southern hemisphere. Retraction and fragmentation of the eastern Australian rainforests from the early Miocene onwards are likely drivers of lineage divergence within sect. facilitating allopatric speciation.
PubMed: 38854888
DOI: 10.3389/fpls.2023.1219354