Conservation of Thermospermine Synthase Activity in Vascular and Non-vascular Plants.
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ABSTRACT:
SUBMITTER: Sole-Gil A
PROVIDER: S-EPMC6579911 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Unlike in flowering plants, the detailed roles of the enzymes in the polyamine (PA) pathway in conifers are poorly known. We explored the sequence conservation of the PA biosynthetic genes and diamine oxidase (DAO) in conifers and flowering plants to reveal the potential functional diversification of the enzymes between the plant lineages. The expression of the genes showing different selective constraints was studied in Scots pine zygotic embryogenesis and early seedling development. We found that the arginine decarboxylase pathway is strongly preferred in putrescine production in the Scots pine as well as generally in conifers and that the reduced use of ornithine decarboxylase (ODC) has led to relaxed purifying selection in ODC genes. Thermospermine synthase (ACL5) genes evolve under strong purifying selection in conifers and the DAO gene is also highly conserved in pines. In developing Scots pine seeds, the expression of both ACL5 and DAO increased as embryogenesis proceeded. Strong ACL5 expression was present in the procambial cells of the embryo and in the megagametophyte cells destined to die via morphologically necrotic cell death. Thus, the high sequence conservation of ACL5 genes in conifers may indicate the necessity of ACL5 for both embryogenesis and vascular development. Moreover, the result suggests the involvement of ACL5 in morphologically necrotic cell death and supports the view of the genetic regulation of necrosis in Scots pine embryogenesis and in plant development. DAO transcripts were located close to the cell walls and between the walls of adjacent cells in Scots pine zygotic embryos and in the roots of young seedlings. We propose that DAO, in addition to the role in Put oxidation for providing H2O2 during the cell-wall structural processes, may also participate in cell-to-cell communication at the mRNA level. To conclude, our findings indicate that the PA pathway of Scots pines possesses several special functional characteristics which differ from those of flowering plants.
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Project description:ACAULIS5 (ACL5) encodes thermospermine synthase in Arabidopsis and its loss-of-function mutant acl5 shows excess xylem differentiation and severe dwarfism. SAC51 encodes a basic helix-loop-helix (bHLH) protein and was identified from sac51-d, a dominant suppressor mutant of acl5, which restores the wild-type phenotype without thermospermine. The 5' leader of the SAC51 mRNA contains multiple upstream open-reading frames (uORFs) and sac51-d has a premature stop codon in the fourth uORF. This uORF is conserved among SAC51 family genes in vascular plants. According to the GUS reporter assay, the SAC51 promoter was not responsive to thermospermine but the SAC51 5' leader fused to the constitutive 35S promoter enhanced the GUS activity in response to thermospermine. Disruption experiments of each start codon of the SAC51 uORFs revealed that uORF4 and uORF6 whose start codon corresponds to the second methionine codon of uORF4 had an inhibitory effect on the main ORF translation while the other four uORFs rather had a stimulatory effect. The response of the 5' leader to thermospermine was retained after disruption of each one of six start codons of these uORFs but abolished by mutating both uORF4 and uORF6 start codons, suggesting the importance of the C-terminal sequence shared by these uORFs in the action of thermospermine. We introduced GUS fusions with 5' leaders of SAC51 family genes from other angiosperm species into Arabidopsis and found that all 5' leaders responsive to thermospermine, so far examined, contained these two conserved, and overlapping uORFs.
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2024-08-16 | GSE241827 | GEO
Project description:BackgroundThe non-native vascular plants of Murmansk Region (European Russia) are under active investigation towards the compilation of the first complete checklist. This work is part of the project 'Flora of Russian Lapland', which ultimately aims at the complete inventory of the taxonomy, distribution and status of vascular plant species in Murmansk Region, based on the comprehensive database of herbarium specimens, field observations and literature.New informationNew territory-level records of non-native vascular plants emerged during our inventory of herbarium collections and recent fieldwork. Fourteen species (Anthemisruthenica, Aruncusdioicus, Bromuscommutatus, Chaerophyllumhirsutum, Galegaorientalis, Geumaleppicum, Leonurusquinquelobatus, Lepidiumdensiflorum, Levisticumofficinale, Myrrhisodorata, Phleumphleoides, Prunusarmeniaca, Rorippasylvestris, Seneciovernalis) are reported as new to Murmansk Region. The historical occurrences of alien plants appeared in the territory largely as contaminants (of seed or forage). In particular, Rorippasylvestris and Seneciovernalis arrived with the forage imported during the Second World War. All recent occurrences originated by escape from confinement (ornamental purposes, horticulture, agriculture), reflecting a high diversity of the modern assortment of cultivated plants in commerce and private gardens. Regarding the invasion status, five alien species are considered casual and eight species are treated as locally established or persisting (for uncertain time). Only one species, Galegaorientalis, is considered naturalised and capable of further spreading in the territory, although without invasive potential.
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Project description:In nature, plants experience large fluctuations in light intensity and they need to balance the absorption and utilization of this energy appropriately. Non-photochemical quenching (NPQ) is a rapidly switchable mechanism that protects plants from photodamage caused by high light exposure by dissipating the excess absorbed energy as heat. It is triggered by the pH gradient across the thylakoid membrane and requires the protein PsbS and the xanthophyll zeaxanthin. However, the site and mechanism of the quencher(s) remain unknown. Here, we constructed a mutant of Arabidopsis thaliana that lacks light-harvesting complex II (LHCII), the main antenna complex of plants, to verify its contribution to NPQ. The mutant plant has normally stacked thylakoid membranes, displays no upregulation of other LHCs but shows a relative decrease in Photosystem I (PSI), which compensates for the decrease of the PSII antenna. The mutant plant exhibits a reduction in NPQ of about 60% and the remaining NPQ resembles that of mutant plants lacking chlorophyll (Chl) b, which lack all PSII peripheral antenna complexes. We thus report that PsbS-dependent NPQ occurs mainly in LHCII, but there is an additional quenching site in the PSII core.
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Project description:Polyamines are linear polycationic compounds that play a crucial role in the growth and development of higher plants. One triamine (spermidine, SPD) and two tetraamine isomers (spermine, SPM, and thermospermine, TSPM) are obtained by the transfer of the aminopropyl group from decarboxylated S-adenosylmethionine to putrescine and SPD. These reactions are catalyzed by the specialized aminopropyltransferases. In that respect, plants are unique eukaryotes that have independently evolved two enzymes, thermospermine synthase (TSPS), encoded by the gene ACAULIS5, and spermine synthase, which produce TSPM and SPM, respectively. In this work, we structurally characterize the ACAULIS5 gene product, TSPS, from the model legume plant Medicago truncatula (Mt). Six crystal structures of MtTSPS - one without ligands and five in complexes with either reaction substrate (SPD), reaction product (TSPM), or one of three cofactor analogs (5'-methylthioadenosine, S-adenosylthiopropylamine, and adenosine) - give detailed insights into the biosynthesis of TSPM. Combined with small-angle X-ray scattering data, the crystal structures show that MtTSPS is a symmetric homotetramer with an interdomain eight-stranded β-barrel. Such an assembly and the presence of a hinge-like feature between N-terminal and C-terminal domains give the protein additional flexibility which potentially improves loading substrates and discarding products after the catalytic event. We also discuss the sequence and structural features around the active site of the plant aminopropyltransferases that distinguish them from each other and determine their characteristic substrate discrimination.
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Project description:Arabidopsis thaliana polyamine oxidase 5 gene (AtPAO5) functions as a thermospermine (T-Spm) oxidase. Aerial growth of its knock-out mutant (Atpao5-2) is significantly repressed by low dose(s) of T-Spm but not by other polyamines. Massive analysis of 3â-cDNA ends (MACE) was performed. Cell wall, lipid and secondary metabolisms were dramatically affected in low dose T-Spm-treated Atpao5-2. Intriguingly Fe-deficient responsive genes and drought stress-induced genes were up-regulated, suggesting that vascular system loses the function. Histological observation showed that vascular system of the joint part between stem and leaves was structurally destroyed. The results indicate that T-Spm homeostasis by a balance of synthesis and catabolism, catalysed by AtPAO5 in Arabidopsis, is important for maintaining vascular system. Phylogenetic analysis showed that PAOs from vascular plants are classified into four clades (I-IV) and AtPAO5 belongs to the clade III. Clade III members show high identity to metazoan PAOs and are not found in non-vascular plants. Furthermore, all the clade III genes are intron-less or contain a single intron whereas the other three clade genes usually contain 7 to 9 introns. The data suggest the occurrence of a horizontal gene transfer of ancestral clade III PAO gene(s) from primitive animals. Fine tuning of T-Spm metabolism is critical for vascular plants and its catabolic gene was acquired from a certain Metazoan to equip the vascular system. 8 Samples analyzed by MACE (Massive Analysis of cDNA ends)
2016-02-22 | E-GEOD-69510 | biostudies-arrayexpress
Project description:Cardiolipin (CL) is an anionic phospholipid at the inner mitochondrial membrane (IMM) that facilitates the formation of transient non-bilayer (non-lamellar) structures to maintain mitochondrial integrity. CL modulates mitochondrial functions including ATP synthesis. However, the biophysical mechanisms by which CL generates non-lamellar structures and the extent to which these structures contribute to ATP synthesis remain unknown. We hypothesized that CL and ATP synthase facilitate the formation of non-bilayer structures at the IMM to stimulate ATP synthesis. By using 1H NMR and 31P NMR techniques, we observed that increasing the temperature (8°C to 37°C), lowering the pH (3.0), or incubating intact mitochondria with CTII - an IMM-targeted toxin that increases the formation of immobilized non-bilayer structures - elevated the formation of non-bilayer structures to stimulate ATP synthesis. The F0 sector of the ATP synthase complex can facilitate the formation of non-bilayer structures as incubating model membranes enriched with IMM-specific phospholipids with exogenous DCCD-binding protein of the F0 sector (DCCD-BPF) elevated the formation of immobilized non-bilayer structures to a similar manner as CTII. Native PAGE assays revealed that CL, but not other anionic phospholipids, specifically binds to DCCD-BPF to promote the formation of stable lipid-protein complexes. Mechanistically, molecular docking studies identified two lipid binding sites for CL in DCCD-BPF. We propose a new model of ATP synthase regulation in which CL mediates the formation of non-bilayer structures that serve to cluster protons and ATP synthase complexes as a mechanism to enhance proton translocation to the F0 sector, and thereby increase ATP synthesis.
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