RESUMO
The tight connection between the deterioration of xylem function and plant mortality under drought is well recognized. However, a lack of mechanistic understanding of how substantial conductivity loss influences plant performance under drought and during post-drought recovery hinders our ability to model tree responses to drought stress. We artificially induced a loss of 50% of xylem conducting area in Scots pine and Norway spruce saplings by stem notching and investigated plant performance under drought and during post-drought recovery. Plant mortality, xylem hydraulic conductivity, leaf water status and stomatal conductance were measured. We observed no preferential mortality of top plant parts (above the notches) compared to basal plant parts (below the notches), and no consistent trend in hydraulic conductivity loss was observed between top and basal parts of dying plants. Stem hydraulic conductivity, water status of the needles and stomatal conductance changed similarly between the top and basal parts during drought and post-drought recovery, which indicated the substantial hydraulic overcapacity of the stems. The recovery of stomatal conductance demonstrated prominent hysteresis due to non-hydraulic stomatal limitations. The results obtained are highly important for modelling the influence of plant hydraulic impairment on plant performance under drought and during post-drought recovery.
Assuntos
Pinus sylvestris , Estômatos de Plantas , Estômatos de Plantas/fisiologia , Secas , Resistência à Seca , Folhas de Planta/fisiologia , Água/fisiologia , Árvores/fisiologia , Noruega , Xilema/fisiologiaRESUMO
We investigated the influence of 40 days of drought on growth, storage processes and primary photosynthetic processes in 3-month-old Scots pine and Norway spruce seedlings growing in perlite culture. Water stress significantly affected seedling water status, whereas absolute dry biomass growth was not substantially influenced. Water stress induced an increase in non-structural carbohydrate content (sugars, sugar alcohols, starch) in the aboveground part of pine seedlings in contrast to spruce seedlings. Due to the relatively low content of sugars and sugar alcohols in seedling organs, their expected contribution to osmotic potential changes was quite low. In contrast to biomass accumulation and storage, photosynthetic primary processes were substantially influenced by water shortage. In spruce seedlings, PSII was more sensitive to water stress than PSI. In particular, electron transport in PSI was stable under water stress despite the substantial decrease of electron transport in PSII. The increase in thermal energy dissipation due to enhancement of non-photochemical quenching (NPQ) was evident in both species under water stress. Simultaneously, the yields of non-regulated energy dissipation in PSII were decreased in pine seedlings under drought. A relationship between growth, photosynthetic activities and storage processes is analysed under weak water deficit.
Assuntos
Fotossíntese/fisiologia , Picea/crescimento & desenvolvimento , Picea/fisiologia , Plântula/crescimento & desenvolvimento , Plântula/fisiologia , Fotoquímica , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , ÁguaRESUMO
BACKGROUND: The genus Bordetella consists of nine species that include important respiratory pathogens such as the 'classical' species B. bronchiseptica, B. pertussis and B. parapertussis and six more distantly related and less extensively studied species. Here we analyze sequence diversity and gene content of 128 genome sequences from all nine species with focus on the evolution of virulence-associated factors. RESULTS: Both genome-wide sequence-based and gene content-based phylogenetic trees divide the genus into three species clades. The phylogenies are congruent between species suggesting genus-wide co-evolution of sequence diversity and gene content, but less correlated within species, mainly because of strain-specific presence of many different prophages. We compared the genomes with focus on virulence-associated genes and identified multiple clade-specific, species-specific and strain-specific events of gene acquisition and gene loss, including genes encoding O-antigens, protein secretion systems and bacterial toxins. Gene loss was more frequent than gene gain throughout the evolution, and loss of hundreds of genes was associated with the origin of several species, including the recently evolved human-restricted B. pertussis and B. holmesii, B. parapertussis and the avian pathogen B. avium. CONCLUSIONS: Acquisition and loss of multiple genes drive the evolution and speciation in the genus Bordetella, including large scale gene loss associated with the origin of several species. Recent loss and functional inactivation of genes, including those encoding pertussis vaccine components and bacterial toxins, in individual strains emphasize ongoing evolution.
Assuntos
Bordetella/classificação , Bordetella/genética , Evolução Molecular , Genoma Bacteriano , Fatores de Virulência/genética , Animais , Sistemas de Secreção Bacterianos/genética , Infecções por Bordetella/microbiologia , Conjuntos de Dados como Assunto , Genes Bacterianos , Variação Genética , Genômica , Genótipo , Humanos , Tipagem de Sequências Multilocus , Filogenia , Polimorfismo de Nucleotídeo ÚnicoRESUMO
Bordetella hinzii is known to cause respiratory disease in poultry and has been associated with a variety of infections in immunocompromised humans. In addition, there are several reports of B. hinzii infections in laboratory-raised mice. Here we sequenced and analysed the complete genome sequences of multiple B. hinzii-like isolates, obtained from vendor-supplied C57BL/6 mice in animal research facilities on different continents, and we determined their taxonomic relationship to other Bordetella species. The whole-genome based and 16S rRNA gene based phylogenies each identified two separate clades in B. hinzii, one was composed of strains isolated from poultry, humans and a rabbit whereas the other clade was restricted to isolates from mice. Distinctly different estimated DNA-DNA hybridization values, average nucleotide identity scores, gene content, metabolic profiles and host specificity all provide compelling evidence for delineation of the two species, B. hinzii - from poultry, humans and rabbit - and Bordetella pseudohinzii sp. nov. type strain 8-296-03T (=NRRL B-59942T=NCTC 13808T) that infect mice.
Assuntos
Bordetella/classificação , Camundongos Endogâmicos C57BL/microbiologia , Filogenia , Animais , Técnicas de Tipagem Bacteriana , Composição de Bases , Bordetella/genética , Bordetella/isolamento & purificação , DNA Bacteriano/genética , Ácidos Graxos/análise , Humanos , Camundongos , Hibridização de Ácido Nucleico , Aves Domésticas , RNA Ribossômico 16S/genética , Coelhos , Análise de Sequência de DNARESUMO
BACKGROUND: Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated genes (cas) are widely distributed among bacteria. These systems provide adaptive immunity against mobile genetic elements specified by the spacer sequences stored within the CRISPR. METHODS: The CRISPR-Cas system has been identified using Basic Local Alignment Search Tool (BLAST) against other sequenced and annotated genomes and confirmed via CRISPRfinder program. Using Polymerase Chain Reactions (PCR) and Sanger DNA sequencing, we discovered CRISPRs in additional bacterial isolates of the same species of Bordetella. Transcriptional activity and processing of the CRISPR have been assessed via RT-PCR. RESULTS: Here we describe a novel Type II-C CRISPR and its associated genes-cas1, cas2, and cas9-in several isolates of a newly discovered Bordetella species. The CRISPR-cas locus, which is absent in all other Bordetella species, has a significantly lower GC-content than the genome-wide average, suggesting acquisition of this locus via horizontal gene transfer from a currently unknown source. The CRISPR array is transcribed and processed into mature CRISPR RNAs (crRNA), some of which have homology to prophages found in closely related species B. hinzii. CONCLUSIONS: Expression of the CRISPR-Cas system and processing of crRNAs with perfect homology to prophages present in closely related species, but absent in that containing this CRISPR-Cas system, suggest it provides protection against phage predation. The 3,117-bp cas9 endonuclease gene from this novel CRISPR-Cas system is 990 bp smaller than that of Streptococcus pyogenes, the 4,017-bp allele currently used for genome editing, and which may make it a useful tool in various CRISPR-Cas technologies.
Assuntos
Bordetella/enzimologia , Bordetella/genética , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Endonucleases/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Composição de Bases/genética , Endonucleases/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
During a succession of phocine morbillivirus outbreaks spanning the past 25 years, Bordetella bronchiseptica was identified as a frequent secondary invader and cause of death. The goal of this study was to evaluate genetic diversity and the molecular basis for host specificity among seal isolates from these outbreaks. MLST and PvuII ribotyping of 54 isolates from Scottish, English or Danish coasts of the Atlantic or North Sea revealed a single, host-restricted genotype. A single, novel genotype, unique from that of the Atlantic and North Sea isolates, was found in isolates from an outbreak in the Caspian Sea. Phylogenetic analysis based either on MLST sequence, ribotype patterns or genome-wide SNPs consistently placed both seal-specific genotypes within the same major clade but indicates a distinct evolutionary history for each. An additional isolate from the intestinal tract of a seal on the south-west coast of England has a genotype otherwise found in rabbit, guinea pig and pig isolates. To investigate the molecular basis for host specificity, DNA and predicted protein sequences of virulence genes that mediate host interactions were used in comparisons between a North Sea isolate, a Caspian Sea isolate and each of their closest relatives as inferred from genome-wide SNP analysis. Despite their phylogenetic divergence, fewer nucleotide and amino acid substitutions were found in comparisons of the two seal isolates than in comparisons with closely related strains. These data indicate isolates of B. bronchiseptica associated with respiratory disease in seals comprise unique, host-adapted and highly clonal populations.
Assuntos
Infecções por Bordetella/veterinária , Bordetella bronchiseptica/genética , Bordetella bronchiseptica/isolamento & purificação , Infecções Respiratórias/veterinária , Focas Verdadeiras/microbiologia , Animais , Infecções por Bordetella/microbiologia , Bordetella bronchiseptica/classificação , Bordetella bronchiseptica/fisiologia , Genótipo , Cobaias , Especificidade de Hospedeiro , Tipagem de Sequências Multilocus , Filogenia , Coelhos , Infecções Respiratórias/microbiologia , Suínos , Doenças dos Suínos/microbiologiaRESUMO
Commercial poultry is an important agricultural industry worldwide. Although dense living conditions and large flocks increase meat and egg production, they also increase the risk of disease outbreaks and zoonoses. Current pathogen identification methods mostly rely on culture-dependent techniques and, therefore, are limited to a very small number of bacteria present in the environment. Next Generation Sequencing allows for culture-independent characterization of lower respiratory microbiome of birds including the identification of novel commensals and potentially emerging pathogens. In this study, we collected tracheo-bronchoalveolar lavage of 14 birds raised at 3 different farms in the Punjab province of Pakistan. To characterize the lower respiratory microbiome of these birds, we sequenced hyper-variable regions of the 16S ribosomal subunit gene. Although dominated by bacteria belonging to a small number of taxonomic classifications, the lower respiratory microbiome from each farm was far more diverse and novel than previously known. The differences in microbiome among farms suggest that inter-farm differences affect the microbiome of birds more than breed, geographic location, or management system. The presence of potential and known pathogens in genetically similar specialty breeds of chickens kept at unnaturally high densities and under variable conditions presents an extraordinary opportunity for the selection of highly pathogenic bacteria. In some instances, opportunistic respiratory pathogens were observed in apparently healthy birds. Understanding and monitoring the respiratory microbiome of such populations may allow the early detection of future disease threats.
Assuntos
Bactérias/classificação , Galinhas/microbiologia , Microbiota , Animais , Bactérias/isolamento & purificação , Lavagem Broncoalveolar/veterinária , DNA Bacteriano/genética , Feminino , Sequenciamento de Nucleotídeos em Larga Escala/veterinária , Pulmão/microbiologia , Masculino , Dados de Sequência Molecular , Paquistão , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA/veterinária , Traqueia/microbiologiaRESUMO
Delayed or incomplete recovery of gas exchange after water stress relief limits assimilation in the post-drought period and can thus negatively affect the processes of post-drought recovery. Abscisic acid (ABA) accumulation and antagonistic action between ABA and cytokinins (CKs) play an important role in regulation of stomatal conductance under water deficit. Specifically, in pine species, sustained ABA accumulation is thought to be the main cause of delayed post-drought gas exchange recovery, although the role of CKs is not yet known. Therefore, we aimed to study the effects of ABA and CKs on recovery of stomatal conductance in greenhouse-grown 3-year-old Scots pine saplings recovering from water stress. We analysed both changes in endogenous ABA and CK contents and the effects of treatment with exogenous CK on stomatal conductance. Drought stress suppressed stomatal conductance, and post-drought stomatal conductance remained suppressed for 2 weeks after plant rewatering. ABA accumulated during water stress, but ABA levels decreased rapidly after rewatering. Additionally, trans-zeatin/ABA and isopentenyladenine/ABA ratios, which were decreased in water-stressed plants, recovered rapidly in rewatered plants. Spraying plants with 6-benzylaminopurine (0.1-100 µM) did not influence recovery of either stomatal conductance or needle water status. It can be concluded that the delayed recovery of stomatal conductance in Scots pine needles was not due to sustained ABA accumulation or a sustained decrease in the CK/ABA ratio, and CK supplementation was unable to overcome this delayed recovery.
Assuntos
Ácido Abscísico , Citocininas , Ácido Abscísico/farmacologia , Citocininas/farmacologia , Resistência à Seca , Desidratação , Estômatos de Plantas , PlantasRESUMO
Forest trees are subjected to multiple stressors during their long lifetime and therefore require effective and finely regulated stress-protective systems. Stressors can induce protective systems either directly or with the involvement of stress memory mechanisms. Stress memory has only begun to be uncovered in model plants and is unexplored in coniferous species. Therefore, we studied the possible role of stress memory in the regulation of the accumulation of stress-protective compounds (heat shock proteins, dehydrins, proline) in the needles of naturally grown Scots pine and Norway spruce trees subjected to the subsequent action of long-term (multiyear) and short-term (seasonal) water shortages. Although the water deficit was relatively mild, it significantly influenced the pattern of expression of stress memory-related heat shock factor (HSF) and SWI/SNF genes, indicating the formation of stress memory in both species. In spruce, dehydrin accumulation was increased by water shortage in a manner compatible with Type II stress memory. The accumulation of HSP40 in spruce needles was positively influenced by long-term water shortage, but this increase was unlikely to be of biological importance due to the concomitant decrease in HSP70, HSP90 and HSP101 accumulation. Finally, proline accumulation was negatively influenced by short-term water deficit in spruce. In pine, no one protective compound accumulated in response to water stress. Taken together, the results indicate that the accumulation of stress-protective compounds was generally independent of stress memory effects both in pine and in spruce.
Assuntos
Picea , Pinus sylvestris , Pinus , Secas , Picea/metabolismo , Plântula/metabolismo , Pinus sylvestris/metabolismoRESUMO
Manganese deficiency is a serious plant nutritional disorder, resulting in the loss of crop productivity in many parts of the world. Despite the progress made in the study of angiosperms, the demand for Mn in gymnosperms and the physiological responses to Mn deficiency remain unexplored. We studied the influence of Mn deficiency for 24 weeks on Pinus sylvestris L. seedling growth, ion homeostasis, pigment contents, lipid peroxidation, chlorophyll fluorescence indices and the transcript levels of photosynthetic genes and genes involved in chlorophyll biosynthesis. It was shown that Mn-deficient plants demonstrated suppressed growth when the Mn content in the needles decreased below 0.34 µmol/g DW. The contents of photosynthetic pigments decreased when the Mn content in the needles reached 0.10 µmol/g DW. Mn deficiency per se did not lead to a decrease in the nutrient content in the organs of seedlings. Photoinhibition of PSII was observed in Mn-deficient plants, although this was not accompanied by the development of oxidative stress. Mn-deficient plants had an increased transcript abundance of genes (psbO, psbP, psbQ, psbA and psbC), encoding proteins directly associated with the Mn cluster also as other proteins involved in photosynthesis, whose activities do not depend on Mn directly. Furthermore, the transcript levels of the genes encoding the large subunit of Rubisco, light-dependent NADPH-protochlorophyllide oxidoreductase and subunits of light-independent protochlorophyllide reductase were also increased in Mn-deficient plants.
Assuntos
Pinus sylvestris , Plântula , Plântula/metabolismo , Manganês/metabolismo , Fotossíntese/genética , Pinus sylvestris/genética , Pinus sylvestris/metabolismo , PlantasRESUMO
The deterioration of plant mineral nutrition during drought is a significant factor in the negative influence of drought on plant performance. We aimed to study the effects of seasonal and multiyear water shortages on nutrient supply and demand in Scots pine and Norway spruce. We studied pine and spruce trees naturally grown in the Bryansk region (Russia). The dynamics of several nutrients (K, Ca, Mg, P, Fe, Mn, Zn, and Ca) in wood, needles, and bark of current-year twigs and the dynamics of the available pools of these elements at different soil depths were analysed. To assess the physiological consequences of changes in element concentrations, lipid peroxidation products and photosynthetic pigments were measured in the needles. Water shortage increased the wood concentrations of all elements except for Mn. In pine, this increase was mainly due to seasonal water deficit, whereas in spruce, multiyear differences in water supply were more important. This increased availability of nutrients was not observed in soil-based analyses. In needles, quite similar patterns of changes were found between species, with Mg increasing almost twofold and Fe and Mn decreasing under water shortage, whereas the remainder of the elements did not change much under differing water supplies. Neither the concentrations of photosynthetic pigments nor the contents of lipid peroxidation products correlated with element dynamics in needles. In summary, water shortage increased the availability of all elements except Mn for the plant; however, needle element contents were regulated independently of element availability for plants.
RESUMO
The toxic effects of heavy metals pose a significant threat to the productivity and stability of forest ecosystems. Changes in the agrochemical properties of polluted forest soils due to global climate changes can increase the bioavailability of previously immobilized heavy metals. To test this hypothesis, we studied the effects of short-term shock exposure to ZnSO4 (50, 150, 300 µM) or CuSO4 (2.5, 5, 10 µM) in hydroculture on 4- to 6-week-old seedlings of Scots pine (Pinus sylvestris L.) with well-developed root systems. The effects of the excess heavy metals on mineral nutrients and the functioning of low-molecular-weight antioxidants and glutathione in protecting plants from oxidative damage were studied. Even short-term exposure to exogenous metals led to their rapid accumulation in the root system and their subsequent transport to aboveground organs. An increase in the 4-hydroxyalkenals content in seedling needles exposed to excess Cu led to an increase in the content of proanthocyanidins and catechins, which act as scavengers of reactive oxygen species. The impact of both metals led to the rapid development of mineral nutrient imbalances in the seedlings, which were most pronounced in the presence of excess Zn. Exposure to excess Zn led to a disruption in the translocation of Fe and a decrease in the Fe content in the needles. The most dramatic consequence of Zn exposure was the development of Mn deficiency in the roots, which was the likely cause of the inhibition of phenolic compound synthesis. A deficiency in phenolic compounds can have serious environmental consequences for pine populations that are at risk of contamination by Zn and Cu salts.
Assuntos
Pinus sylvestris , Poluentes do Solo , Antioxidantes , Cobre/análise , Cobre/toxicidade , Ecossistema , Nutrientes , Plântula/química , Poluentes do Solo/análise , Poluentes do Solo/toxicidade , Água , Zinco/toxicidadeRESUMO
Dehydrins are well-known components of plant responses to different stresses that cause dehydration, including drought, freezing, salinity, etc. In conifers, the dehydrin gene family is very large, implying that the members of this family have important physiological functions in conifer stress tolerance. However, dehydrin gene expression displays a wide range of responses to stress, from thousand-fold increased expression to decreased expression, and it is generally unknown how regulatory systems are connected at the mRNA and protein levels. Therefore, we studied these aspects of dehydrin regulation in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst) seedlings under polyethylene glycol 6000-induced osmotic stress ranging from relatively low (culture medium water potential of -0.15 MPa) to very high (-1.0 MPa) intensities. In pine, the major dehydrin protein was Dhn1 in both the roots and needles, and in spruce, two isoforms of the Dhn4 protein were the major dehydrins; both of these proteins are AESK-type dehydrins. The genes encoding these major proteins were highly expressed even under control conditions; surprisingly, we also observed several highly expressed dehydrin genes that were not abundantly translated. Under osmotic stress, the most prominent expression changes were observed for the dehydrin genes with low basal expression levels, whereas highly expressed genes generally demonstrated rather modest changes in expression. We report proposed constitutive physiological functions of the AESK-type dehydrins in Pinaceae plants.
Assuntos
Picea , Pinus sylvestris , Pinus , Picea/genética , Pinus sylvestris/genética , Plântula/genética , ÁguaRESUMO
Different plant hormones are involved in plant adaptation to water deficit. In comparison to angiosperms, little is known about the impact of drought on the pool of phytohormones in gymnosperms. Therefore, we studied the effect of polyethylene glycol-induced water deficit on the changes in content of different phytohormones in Scots pine and Norway spruce seedlings, which are known for their different strategies of adaptation to water deficit. The following hormone classes were analysed: cytokinins, auxins, jasmonates, salicylic and benzoic acids, and 1-aminocyclopropane-1-carboxylic acid (an ethylene precursor). No consistent reaction to water stress was observed for the content of well-known stress-related hormones - salicylic acid and jasmonates. In contrast, drought induced a dose-dependent accumulation of cytokinins in pine needles, with less profound changes in spruce needles. The most prominent changes were observed for 1-aminocyclopropane-1-carboxylic acid content, which increased several-fold in spruce roots and pine needles under water deficit. Water-deficit-induced changes in the contents of cytokinins and 1-aminocyclopropane-1-carboxylic acid were accompanied by the differential regulation of genes involved in the metabolism of these hormones. Possible links between changes in hormone pools and the adaptation of seedlings to water deficit are discussed.
Assuntos
Picea , Pinus sylvestris , Reguladores de Crescimento de Plantas , Plântula , Estresse Fisiológico , Transcriptoma , Secas , Regulação da Expressão Gênica de Plantas , Picea/genética , Pinus sylvestris/genética , Reguladores de Crescimento de Plantas/genética , Plântula/genética , Estresse Fisiológico/genética , Água/metabolismoRESUMO
Abscisic acid (ABA) is one of the main participants in the regulation of plant responses to water deficiency. Knowledge of the ABA signal transduction pathways in gymnosperms is rather limited, especially in comparison with those in angiosperms. Seedlings of Scots pine and Norway spruce are known for their contrasting behaviour strategies under water deficit. To characterize the possible role of ABA in these differences, ABA dynamics were investigated under conditions of water deficit in seedlings of these two species. The content of ABA and its catabolites was followed in the roots and needles of seedlings of Pinus sylvestris and Picea abies under conditions of polyethylene glycol (PEG)-induced water deficiency (-0.15 and -0.5â¯MPa) for 10 days. The expression of the main genes for ABA-biosynthetic enzymes was also analysed. ABA showed more pronounced stress-dependent dynamics in pine roots than in spruce roots, whereas in needles, the response was greater for spruce than pine. The ABA increase during drought was mainly due to de novo synthesis and the shift in the balance between ABA synthesis and catabolism towards synthesis. The ABA-glucosyl ester did not serve as a reserve for the release of free ABA under water deficiency. The expression levels of the main ABA biosynthetic genes showed a weak or no correlation with changes in ABA content under water stress, i.e., the ABA content in the seedlings of both species was not directly linked to the transcript levels of the main ABA biosynthetic genes. Less-pronounced stress-induced changes in ABA in pine needles than in spruce needles may be related to pine seedlings having a less conservative strategy of growth and maintenance of water balance under water deficit.
Assuntos
Ácido Abscísico/metabolismo , Secas , Picea/metabolismo , Pinus sylvestris/metabolismo , Desidratação , Picea/efeitos dos fármacos , Pinus sylvestris/efeitos dos fármacos , Polietilenoglicóis/farmacologia , Plântula/efeitos dos fármacos , Plântula/metabolismoRESUMO
Stressors of different natures, including drought stress, substantially compromise the ability of plants to effectively and safely utilize light energy. We investigated the influence of water stress on the photosynthetic processes in Picea abies and Pinus sylvestris, two species with contrasting drought sensitivities. Spruce and pine seedlings were exposed to polyethylene glycol 6000-induced water deficits of different intensities and durations. The maintenance of photosystem I (PSI) oxidation in spruce required increased photosynthetic control and led to the increased reduction of the plastoquinone pool, which was not the case in pine seedlings. As a result of increased excitation pressure, photosystem II (PSII) inactivation was observed in spruce plants, whereas in pine, the decreased PSII photochemistry was likely due to sustained non-photochemical quenching. Downregulation of PSII photochemistry and maintenance of PSI in an oxidized state were linked with the prevention of oxidative stress, even under severe water deficit. The decreased photosynthetic pigment content and photosynthetic gene expression suggested the coordinated downregulation of photosynthetic apparatus components under water stress to reduce light energy absorption. In summary, the observed adaptative mechanisms of pine and spruce to water stress may be similar to the well-studied adaptative mechanisms to winter stress, which may indicate the universality of protective mechanisms under various stresses in conifers.
Assuntos
Secas , Fotossíntese , Picea/metabolismo , Pinus sylvestris/metabolismo , Peroxidação de Lipídeos , Fotossíntese/genética , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/metabolismo , Plântula/metabolismoRESUMO
We investigated physiological responses of 7-week-old Norway spruce seedlings to water deficits of different intensities. Hydroponically grown seedlings were subjected to mild (-0.15 MPa), strong (-0.5 and -1.0 MPa) and extreme (-1.5 MPa) water deficit induced by polyethylene glycol 6000, and their growth parameters, water status and physiological activity were analyzed. Seedlings effectively restricted water loss under drought, and even under extreme water deficit, shoot relative water content did not fall below 85%. Water stress induced substantial decreases in the osmotic potentials of root and needle cell sap, up to 0.3-0.4 MPa under extreme water deficit, though this did not result from water loss or accumulation of K+ and Na+ ions. Seedling growth was very susceptible to water stress because of poor capacity for cell wall adjustment. Water stress injured seedling roots, as evidenced by the loss of root cell physiological activity estimated by the ability to hydrolyse fluorescein diacetate and by increased root calcium content up to 8-10-fold under extreme water stress. At the same time, root hair growth was enhanced, especially under mild water deficit, which increased the root water-absorbing capacity. In summary, seedlings of Norway spruce were characterized by high susceptibility to water stress and concurrently by pronounced ability to maintain water status. These characteristics are fully consistent with spruce confinement to moist habitats.
Assuntos
Polietilenoglicóis/química , Plântula/crescimento & desenvolvimento , Sobrevivência Celular , Desidratação , Secas , Ecossistema , Noruega , Osmose , Plântula/química , ÁguaRESUMO
The human pathogen Acinetobacter baumannii has emerged as a frequent cause of hospital-acquired infections, but infection of animals has rarely been observed. Here we analyzed an outbreak of epidemic pneumonia killing hundreds of sheep on a farm in Pakistan and identified A. baumannii as the infecting agent. A pure culture of strain AbPK1 isolated from lungs of sick animals was inoculated into healthy sheep, which subsequently developed similar disease symptoms. Bacteria re-isolated from the infected animals were shown to be identical to the inoculum, fulfilling Koch's postulates. Comparison of the AbPK1 genome against 2283 A. baumannii genomes from the NCBI database revealed that AbPK1 carries genes for unusual surface structures, including a unique composition of iron acquisition genes, genes for O-antigen synthesis and sialic acid-specific acetylases of cell-surface carbohydrates that could enable immune evasion. Several of these unusual and otherwise rarely present genes were also identified in genomes of phylogenetically unrelated A. baumannii isolates from combat-wounded US military from Afghanistan indicating a common gene pool in this geographical region. Based on core genome MLST this virulent isolate represents a newly emerging lineage of Global Clone 2, suggesting a human source for this disease outbreak. The observed epidemic, direct transmission from sheep to sheep, which is highly unusual for A. baumannii, has important consequences for human and animal health. First, direct animal-to-animal transmission facilitates fast spread of pathogen and disease in the flock. Second, it may establish a stable ecological niche and subsequent spread in a new host. And third, it constitutes a serious risk of transmission of this hyper-virulent clone from sheep back to humans, which may result in emergence of contagious disease amongst humans.
RESUMO
We investigated the long-term impact of the largest Russian cement plant on mesopodzol sandy soils and Scots pine stands. We determined the distributions of the total and available pools of Ca, Mg, K, Na, Mn, Fe, Zn, Ni, Cu, Pb and Cd in the soil profile to a depth of 60â¯cm (illuvial horizon) as well as the accumulation patterns of these elements in the vegetative and generative organs of Scots pine trees. High Ca accumulation in the impact zone soils was a result of CaO emissions by a cement plant. Also, CaO became the main cause of soil profile alkalization due to neutralization of soil acids and formation of calcium hydroxide or carbonates. Alkalization immobilized substantial amounts of Fe, Mn, Zn and Ni in the soil, reducing their availability. The most prominent effect of long-term cement production was a prominent Mn deficiency in vegetative and generative Scots pine organs due to the exhaustion of the available Mn pool in the illuvial horizon. The miniaturization of cones, a decrease in seed yield and a reduction in seed germinability were observed in the emission impact zones. Pretreatment of Mn-deficient seeds with manganese eliminated Mn deficiency but did not increase seed germination.
Assuntos
Monitoramento Ambiental , Pinus/química , Poluentes do Solo/análise , Solo/química , Materiais de Construção , Manganês , Metais Pesados/análise , Pinus sylvestris , Federação Russa , Sementes/química , ÁrvoresRESUMO
The morphological, physiological, and biochemical parameters of 6-week-old seedlings of Scots pine (Pinus sylvestris L.) were studied under deficiency (1.2 nM) and chronic exposure to copper (0.32, 1, 2.5, 5, and 10 µM CuSO4) in hydroculture. The deposit of copper in the seed allowed the seedlings to develop under copper deficiency without visible disruption of growth. The high sensitivity of Scots pine to the toxic effects of copper was shown, which manifested as a significant inhibition of growth and development. The loss of dominance of the main root and a strong inhibition of lateral root development pointed to a lack of adaptive reorganization of the root system architecture under copper excess. A preferential accumulation of copper in the root and a minor translocation in aerial organs confirmed that Scots pine belongs to a group of plants that exclude copper. Selective impairment in the absorption of manganese was discovered, under both deficiency and excess of copper in the nutrient solution, which was independent of the degree of development of the root system. Following 10 µM CuSO4 exposure, the absorption of manganese and iron from the nutrient solution was completely suppressed, and the development of seedlings was secured by the stock of these micronutrients in the seed. The absence of signs of oxidative stress in the seedling organs was shown under deficiency and excess of copper, as evidenced by the steady content of malondialdehyde and 4-hydroxyalkenals. Against this background, no changes in total superoxide dismutase activity in the organs of seedlings were revealed, and the increased content of low-molecular-weight antioxidants was observed in the roots under 1 µM and in the needles under 5 µM CuSO4 exposures.