Genes encoding ribosomal RNA (rDNA) are essential for cell survival and are particularly sensitive to factors leading to genomic instability. Their repetitive character makes them prone to inappropriate recombinational events arising from collision of transcriptional and replication machineries, resulting in unstable rDNA copy numbers. In this review, we summarize current knowledge on the structure and organization of rDNA, its role in sensing changes in the genome, and its linkage to aging. We also review recent findings on the main factors involved in chromatin assembly and DNA repair in the maintenance of rDNA stability in the model plants Arabidopsis thaliana and the moss Physcomitrella patens, providing a view across the plant evolutionary tree.
- MeSH
- Arabidopsis genetics MeSH
- DNA, Plant genetics MeSH
- Transcription, Genetic MeSH
- Gene Dosage MeSH
- Humans MeSH
- Bryopsida genetics MeSH
- Genomic Instability MeSH
- DNA Repair * MeSH
- DNA Replication MeSH
- Chromatin Assembly and Disassembly MeSH
- DNA, Ribosomal genetics MeSH
- Aging genetics MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Review MeSH
A passive biomonitoring survey using terrestrial mosses was performed in a heavily polluted industrial region on the border between Czechia and Poland in a regular grid of 41 sampling points. The concentrations of 38 elements were determined in the moss samples, using Neutron Activation Analysis (NAA). Simultaneously, air pollution modelling was performed using the Czech reference methodology Symos'97 for the year of the sampling (2015) and 3 years prior (2012) in order to compare the results of both the approaches and evaluate the credibility of the moss biomonitoring method. The NAA results were transformed according to the principles of compositional data analysis and assessed using hierarchical clustering on principal components. The resulting clusters were compared with the results of air pollution modelling using one-way analysis of variance. The association of determined clusters with the pollution from industrial sources was confirmed only for the results of the 2012 modelling. This validates the complementarity of the air pollution modelling and the moss biomonitoring, ascertains the moss biomonitoring as a valid method for long-term pollution assessment and confirms one of the fundamentals of moss biomonitoring, the reflection of the atmospheric conditions prevailing in the period before the sampling.
- MeSH
- Biological Monitoring MeSH
- Bryophyta * MeSH
- Air Pollutants analysis MeSH
- Bryopsida * MeSH
- Environmental Monitoring MeSH
- Metals, Heavy analysis MeSH
- Air Pollution analysis MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- Poland MeSH
Antioxidative responses of axenic protonema cultures of the moss Physcomitrella patens exposed to 10 μM Cd over 40 d were studied. Cd treatment suppressed growth by ca. 75% with concomitant browning of some filaments and suppression of chlorophyll autofluorescence but had no impact on tissue water content. Despite this negative growth responses which could be related to enhanced ROS formation (as detected using fluorescence staining reagents for total ROS, hydroperoxides and lipid peroxidation), some metabolites revealed strong elevation by Cd which could contribute to attenuation of long-term Cd stress (elevation of ascorbic, malic and citric acids). Molar ratio of malate to Cd was 12.7 and citrate to Cd 2.5, thus potentially contributing to Cd chelation. Interestingly, GSH/GSSG pool and nitric oxide formation remained unaltered by Cd. Accumulation of Cd reached 82 μg/g DW with bioaccumulation factor of 73. Data indicate that Cd induces elevation of potentially protective metabolites even after prolonged exposure though they do not prevent oxidative stress sufficiently.
- MeSH
- Antioxidants metabolism MeSH
- Chlorophyll metabolism MeSH
- Cadmium analysis toxicity MeSH
- Bryopsida drug effects metabolism MeSH
- Oxidative Stress drug effects MeSH
- Hydrogen Peroxide metabolism MeSH
- Lipid Peroxidation drug effects MeSH
- Reactive Oxygen Species metabolism MeSH
- Publication type
- Journal Article MeSH
Heterokonts, Alveolata protists, green algae from Charophyta and Chlorophyta divisions, and all Embryophyta plants possess an aldehyde dehydrogenase (ALDH) gene named ALDH12. Here, we provide a biochemical characterization of two ALDH12 family members from the lower plant Physcomitrella patens and higher plant Zea mays. We show that ALDH12 encodes an NAD+-dependent glutamate γ-semialdehyde dehydrogenase (GSALDH), which irreversibly converts glutamate γ-semialdehyde (GSAL), a mitochondrial intermediate of the proline and arginine catabolism, to glutamate. Sedimentation equilibrium and small-angle X-ray scattering analyses reveal that in solution both plant GSALDHs exist as equilibrium between a domain-swapped dimer and the dimer-of-dimers tetramer. Plant GSALDHs share very low-sequence identity with bacterial, fungal, and animal GSALDHs (classified as ALDH4), which are the closest related ALDH superfamily members. Nevertheless, the crystal structure of ZmALDH12 at 2.2-Å resolution shows that nearly all key residues involved in the recognition of GSAL are identical to those in ALDH4, indicating a close functional relationship with ALDH4. Phylogenetic analysis suggests that the transition from ALDH4 to ALDH12 occurred during the evolution of the endosymbiotic plant ancestor, prior to the evolution of green algae and land plants. Finally, ALDH12 expression in maize and moss is downregulated in response to salt and drought stresses, possibly to maintain proline levels. Taken together, these results provide molecular insight into the biological roles of the plant ALDH12 family.
This study analyzed the impact of road transportation on the concentration of Zn, Ni, Pb, Co, and Cd in moss (Pleurozium schreberi). The study was carried out over five years near a national road running from the north to the east (Poland) in the area of Natura 2000 sites. Samples were collected at three significantly different locations: (1) near a sharp bend, (2) near a straight section of the road in a woodless area, and (3) in a slightly wooded area. At each location, moss samples were collected from sites situated 2, 4, 6, 8, 10, 12, and 14 m from the road edge. The highest Zn and Cd contents in the moss were recorded 6 m from the road edge near a sharp bend (where vehicles brake sharply and accelerate suddenly). At the same location, at a distance of 2 m, the highest Pb concentration was noted, and at a distance of 4 m from the road, the highest Ni concentration was noted. The Co concentration in the moss was the highest near the woodless straight section at a distance of 2 and 12 m from the road. The concentrations of Zn, Pb, Ni, Co (only at the woodless location), and Cd (at all locations) were significantly and negatively correlated with distance from the road.
- MeSH
- Environmental Biomarkers * MeSH
- Transportation * MeSH
- Bryopsida chemistry MeSH
- Environmental Monitoring methods MeSH
- Metals, Heavy chemistry toxicity MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Poland MeSH
The diverse forms of today's dominant vascular plant flora are generated by the sustained proliferative activity of sporophyte meristems at plants' shoot and root tips, a trait known as indeterminacy [1]. Bryophyte sister lineages to the vascular plants lack such indeterminate meristems and have an overall sporophyte form comprising a single small axis that ceases growth in the formation of a reproductive sporangium [1]. Genetic mechanisms regulating indeterminacy are well characterized in flowering plants, involving a feedback loop between class I KNOX genes and cytokinin [2, 3], and class I KNOX expression is a conserved feature of vascular plant meristems [4]. The transition from determinate growth to indeterminacy during evolution was a pre-requisite to vascular plant diversification, but mechanisms enabling the innovation of indeterminacy are unknown [5]. Here, we show that class I KNOX gene activity is necessary and sufficient for axis extension from an intercalary region of determinate moss shoots. As in Arabidopsis, class I KNOX activity can promote cytokinin biosynthesis by an ISOPENTENYL TRANSFERASE gene, PpIPT3. PpIPT3 promotes axis extension, and PpIPT3 and exogenously applied cytokinin can partially compensate for loss of class I KNOX function. By outgroup comparison, the results suggest that a pre-existing KNOX-cytokinin regulatory module was recruited into vascular plant shoot meristems during evolution to promote indeterminacy, thereby enabling the radiation of vascular plant shoot forms.
Telomeres and ribosomal RNA genes (rDNA) are essential for cell survival and particularly sensitive to factors affecting genome stability. Here, we examine the role of RAD51 and its antagonist, RTEL1, in the moss Physcomitrella patens. In corresponding mutants, we analyse their sensitivity to DNA damage, the maintenance of telomeres and rDNA, and repair of double-stranded breaks (DSBs) induced by genotoxins with various modes of action. While the loss of RTEL1 results in rapid telomere shortening, concurrent loss of both RAD51 genes has no effect on telomere lengths. We further demonstrate here the linked arrangement of 5S and 45S rRNA genes in P. patens. The spacer between 5S and 18S rRNA genes, especially the region downstream from the transcription start site, shows conspicuous clustering of sites with a high propensity to form quadruplex (G4) structures. Copy numbers of 5S and 18S rDNA are reduced moderately in the pprtel1 mutant, and significantly in the double pprad51-1-2 mutant, with no progression during subsequent cultivation. While reductions in 45S rDNA copy numbers observed in pprtel1 and pprad51-1-2 plants apply also to 5S rDNA, changes in transcript levels are different for 45S and 5S rRNA, indicating their independent transcription by RNA polymerase I and III, respectively. The loss of SOL (Sog One-Like), a transcription factor regulating numerous genes involved in DSB repair, increases the rate of DSB repair in dividing as well as differentiated tissue, and through deactivation of G2/M cell-cycle checkpoint allows the cell-cycle progression manifested as a phenotype resistant to bleomycin.
- MeSH
- DNA Helicases genetics metabolism MeSH
- Genetic Loci MeSH
- Bryopsida enzymology genetics MeSH
- Mutation MeSH
- Genomic Instability * MeSH
- Rad51 Recombinase genetics metabolism MeSH
- DNA, Ribosomal genetics MeSH
- RNA, Ribosomal, 18S genetics MeSH
- RNA, Ribosomal, 5S genetics MeSH
- RNA, Ribosomal genetics MeSH
- Plant Proteins genetics metabolism MeSH
- Telomere genetics MeSH
- Transcription Factors genetics metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
: Jasmonic acid (JA) and its related derivatives are ubiquitously occurring compounds of land plants acting in numerous stress responses and development. Recent studies on evolution of JA and other oxylipins indicated conserved biosynthesis. JA formation is initiated by oxygenation of α-linolenic acid (α-LeA, 18:3) or 16:3 fatty acid of chloroplast membranes leading to 12-oxo-phytodienoic acid (OPDA) as intermediate compound, but in Marchantiapolymorpha and Physcomitrellapatens, OPDA and some of its derivatives are final products active in a conserved signaling pathway. JA formation and its metabolic conversion take place in chloroplasts, peroxisomes and cytosol, respectively. Metabolites of JA are formed in 12 different pathways leading to active, inactive and partially active compounds. The isoleucine conjugate of JA (JA-Ile) is the ligand of the receptor component COI1 in vascular plants, whereas in the bryophyte M. polymorpha COI1 perceives an OPDA derivative indicating its functionally conserved activity. JA-induced gene expressions in the numerous biotic and abiotic stress responses and development are initiated in a well-studied complex regulation by homeostasis of transcription factors functioning as repressors and activators.
- MeSH
- Chloroplasts metabolism MeSH
- Cyclopentanes metabolism MeSH
- Species Specificity MeSH
- alpha-Linolenic Acid metabolism MeSH
- Marchantia metabolism MeSH
- Fatty Acids metabolism MeSH
- Bryopsida metabolism MeSH
- Metabolic Networks and Pathways MeSH
- Fatty Acids, Unsaturated metabolism MeSH
- Oxylipins metabolism MeSH
- Peroxisomes metabolism MeSH
- Publication type
- Journal Article MeSH
- Review MeSH
Research in algae usually focuses on the description and characterization of morpho-and phenotype as a result of adaptation to a particular habitat and its conditions. To better understand the evolution of lineages we characterized responses of filamentous streptophyte green algae of the genera Klebsormidium and Zygnema, and of a land plant-the moss Physcomitrellapatens-to genotoxic stress that might be relevant to their environment. We studied the induction and repair of DNA double strand breaks (DSBs) elicited by the radiomimetic drug bleomycin, DNA single strand breaks (SSB) as consequence of base modification by the alkylation agent methyl methanesulfonate (MMS) and of ultra violet (UV)-induced photo-dimers, because the mode of action of these three genotoxic agents is well understood. We show that the Klebsormidium and Physcomitrella are similarly sensitive to introduced DNA lesions and have similar rates of DSBs repair. In contrast, less DNA damage and higher repair rate of DSBs was detected in Zygnema, suggesting different mechanisms of maintaining genome integrity in response to genotoxic stress. Nevertheless, contrary to fewer detected lesions is Zygnema more sensitive to genotoxic treatment than Klebsormidium and Physcomitrella.
- Publication type
- Journal Article MeSH
Auxin steers numerous physiological processes in plants, making the tight control of its endogenous levels and spatiotemporal distribution a necessity. This regulation is achieved by different mechanisms, including auxin biosynthesis, metabolic conversions, degradation, and transport. Here, we introduce cis-cinnamic acid (c-CA) as a novel and unique addition to a small group of endogenous molecules affecting in planta auxin concentrations. c-CA is the photo-isomerization product of the phenylpropanoid pathway intermediate trans-CA (t-CA). When grown on c-CA-containing medium, an evolutionary diverse set of plant species were shown to exhibit phenotypes characteristic for high auxin levels, including inhibition of primary root growth, induction of root hairs, and promotion of adventitious and lateral rooting. By molecular docking and receptor binding assays, we showed that c-CA itself is neither an auxin nor an anti-auxin, and auxin profiling data revealed that c-CA does not significantly interfere with auxin biosynthesis. Single cell-based auxin accumulation assays showed that c-CA, and not t-CA, is a potent inhibitor of auxin efflux. Auxin signaling reporters detected changes in spatiotemporal distribution of the auxin response along the root of c-CA-treated plants, and long-distance auxin transport assays showed no inhibition of rootward auxin transport. Overall, these results suggest that the phenotypes of c-CA-treated plants are the consequence of a local change in auxin accumulation, induced by the inhibition of auxin efflux. This work reveals a novel mechanism how plants may regulate auxin levels and adds a novel, naturally occurring molecule to the chemical toolbox for the studies of auxin homeostasis.
- MeSH
- Arabidopsis drug effects growth & development MeSH
- Cinnamates chemistry metabolism pharmacology MeSH
- Cyclin B genetics metabolism MeSH
- Plants, Genetically Modified MeSH
- Isomerism MeSH
- Plant Roots drug effects growth & development metabolism MeSH
- Indoleacetic Acids metabolism MeSH
- Bryopsida drug effects growth & development MeSH
- Arabidopsis Proteins genetics metabolism MeSH
- Qa-SNARE Proteins genetics metabolism MeSH
- Gene Expression Regulation, Plant MeSH
- Selaginellaceae drug effects growth & development MeSH
- Signal Transduction MeSH
- Publication type
- Journal Article MeSH
