Changes in Eucalyptus camaldulensis essential oil composition as response to drought preconditioning

Abstract

Water deficit, a common constraint in forestry, is the main cause of plant stress during plantation. The survival and growth of seedlings is also compromised by herbivory during establishment. The potential of nursery preconditioning to enhance survival chances of future trees by reducing palatability or attracting beneficial insects as a result of changes in chemical defences may be an answer to overcome this situation. Changes in essential oil production and composition were evaluated by GC and GC-MS in Eucalytus camaldulensis seedlings submitted to drought during four weeks at the last stage of nursery period (20 weeks). Significant changes in essential oil relative composition were found. Seedlings (young leaves) submitted to drought developed a terpenoid blend, which has been previously associated to mature leaves and related to their higher resistance towards herbivory. Total amount of non-oxygenated terpenes decreased by 44%, whereas some oxygenated sesquiterpenes (globulol, epiglobulol and ledol) were doubled, and 1,8-cineole content was enhanced by 28.3%.     

Monoterpene engineering in a woody plant Eucalyptus camaldulensis using a limonene synthase cDNA

Metabolic engineering aimed at monoterpene production has become an intensive research topic in recent years, although most studies have been limited to herbal plants including model plants such as Arabidopsis. The genus Eucalyptus includes commercially important woody plants in terms of essential oil production and the pulp industry. This study attempted to modify the production of monoterpenes, which are major components of Eucalyptus essential oil, by introducing two expression constructs containing Perilla frutescens limonene synthase ( PFLS ) cDNA, whose gene products were designed to be localized in either the plastid or cytosol, into Eucalyptus camaldulensis . The expression of the plastid-type and cytosol-type PFLS cDNA in transgenic E. camaldulensis was confirmed by real-time polymerase chain reaction (PCR). Gas chromatography with a flame ionization detector analyses of leaf extracts revealed that the plastidic and cytosolic expression of PFLS yielded 2.6- and 4.5-times more limonene than that accumulated in wild-type E. camaldulensis , respectively, while the ectopic expression of PFLS had only a small effect on the emission of limonene from the leaves of E. camaldulensis. Surprisingly, the high level of PFLS in Eucalyptus was accompanied by a synergistic increase in the production of 1,8-cineole and α-pinene, two major components of Eucalyptus monoterpenes. This genetic engineering of monoterpenes demonstrated a new potential for molecular breeding in woody plants.     

River Red Gum (Eucalyptus camaldulensis Dehnh.) organic matter as a carbon source in the lower Darling River,Australia

The Darling River, in New South Wales, Australia, is a large semi-arid system with a highly variable flow regime, characterised by unpredictable events of flooding and drought. In large lowland rivers like the Darling, lateral (river-floodplain) interactions can greatly influence both physical and biological components of the system. The floodplain and riparian zone of the Darling River is dominated by River Red Gum (RRG), Eucalyptus camaldulensis. The large amount of organic matter they produce accumulates on the floodplain and on benches within the channel, and is subject to alternate periods of flooding and drying as a result of highly variable flows. This paper examines the effect of alternate periods of flooding and drying on the processing of E. camaldulensis organic matter. Results of the 6-month in situ field study, together with results from laboratory experiments comparing dissolved organic carbon (DOC) release from various RRG litter types, suggest that RRG leaves provide the most bio-available source of carbon to the system, while bark may be more important as a habitat for invertebrates and other fauna. Laboratory experiments exploring the effect of drying and re-flooding on litter breakdown and release of DOC suggested that the majority of DOC was released from RRG leaves in the first 24 h of inundation. Also, upon drying and re-flooding of the leaves, a smaller but significant release of DOC occurred. However, an alternative wet/dry cycle did not affect weight loss of the leaf litter. Results of the field and lab experiments suggest that RRG leaves represent an important source of carbon to the Darling River, with inputs being influenced by the highly variable flow regime.     

Mass Propagation of Eucalyptus camaldulensis in a Scaled-up Vessel Under In Vitro Photoautotrophic Condition

A scaled-up culture vessel was designed for the large-scalephotoautotrophic micropropagation of chlorophyllous plants.The culture vessel (volume 20 l) contained a plug cell traywith 448 plantlets, and had a forced ventilation system to supplyCO₂-enriched air. A nutrient-reservoir was connected to theculture vessel from which nutrient solution was circulated tothe culture vessel every 24 h. Nodal leafy cuttings of Eucalyptuscamaldulensis L. were cultured photoautotrophically in thissystem without sugar in the nutrient medium, but with an enrichedCO₂concentration and a high photosynthetic photon flux. Thegrowth and the net photosynthetic rate of the in vitro grownplantlets and the survival percentage of the plantlets aftertransplanting to ex vitro conditions were compared with thoseof plantlets grown photoautotrophically under natural ventilationin conventional small culture vessels (Magenta-type vessels;volume 0.4 l). Fresh and dry masses and net photosynthetic ratewere significantly higher in plantlets grown in the scaled-upvessel compared to plantlets grown in the conventional smallvessels (control). The environmental conditions created in thisscaled-up vessel (with forced ventilation) also facilitatedacclimatizationin vitro . Importantly, after transplanting tothe ex vitro condition, plantlets grew well without any specializedexvitro acclimatization treatment. Copyright 2000 Annals of BotanyCompany CO₂enrichment, Eucalyptus camaldulensis L., ex vitro, forced ventilation, natural ventilation, photoautotrophic, scaled-up vessel, survival percentage     

Phenolic compounds and antioxidants from Eucalyptus camaldulensis as affected by some extraction conditions,a preparative optimization for GC-MS analysis

Abstract

Four organic solvents along with water were applied for the conventional extraction of Eucalyptus camaldulensis (Myrtaceae), phenolic contents and antioxidant activities were investigated through variable protocols and correlation coefficients were considered, the phenolic composition was also characterized by Gas chromatography-mass spectrometry (GC-MS). Using solvents with dissimilar polarities affected the phenolic yields extracted from E. camaldulensis and their related antioxidant activities varied significantly among the four investigated plant organs. The leaf extract of acetone 70% contained the highest amount of phenolic compounds (46.56?mg/g dry weight); while the bud-water boiled extract maintained the maximum value of tannins (45.68?mg/g dry weight). Correlation coefficients indicated that phenolic compounds were mostly accountable for the phosphomolybednum antioxidant potentials (0.520), followed by tannins (0.460). Also, both the reducing power activities and hydrogen peroxide scavenging of E. camaldulensis extracts positively correlated with tannins, but at different significance degrees. However, the GC-MS analysis revealed that most of the detected phenolic constituents were more abundant in the plant seed. So, the existence of some other compounds such as organic acids, along with phenolics, may have increased the antioxidant potentials of leaf and bud. Undeniably, the optimization of extraction conditions could stimulate the antioxidant capabilities of the plant extracts of E. camaldulensis.     

The presence of heartwood decay,a precursor to hollow formation,within Eucalyptus camaldulensis in relation to stem size

River Red Gums (Eucalyptus camaldulensis Dehnh.) are large trees that dominated many of continental Australia's riparian areas, providing abundant hollows for nesting and denning fauna. Land clearing and forestry have reduced the availability of large trees, and much of the remaining forest is dominated by small regrowth trees that lack visible hollow entrances. Inspection of recently felled River Red Gums revealed that heartwood decay, a precursor of hollow formation, can be common in relatively small trees. Internal decay and voids remain inaccessible until stochastic damage exposes them, which may not occur until the tree is old, and hence probably large. This discrepancy indicates that there is likely to be a size range of trees into which artificial entrances can be added to quickly increase hollow availability in landscapes undergoing active restoration as fauna habitat.     

Identification of a Ligand on the Wip1 Bacteriophage Highly Specific for a Receptor on Bacillus anthracis

Tectiviridae is a family of tailless bacteriophages with Gram-negative and Gram-positive hosts. The family model PRD1 and its close relatives all infect a broad range of enterobacteria by recognizing a plasmid-encoded conjugal transfer complex as a receptor. In contrast, tectiviruses with Gram-positive hosts are highly specific to only a few hosts within the same bacterial species. The cellular determinants that account for the observed specificity remain unknown. Here we present the genome sequence of Wip1, a tectivirus that infects the pathogen Bacillus anthracis. The Wip1 genome is related to other tectiviruses with Gram-positive hosts, notably, AP50, but displays some interesting differences in its genome organization. We identified Wip1 candidate genes for the viral spike complex, the structure located at the capsid vertices and involved in host receptor binding. Phage adsorption and inhibition tests were combined with immunofluorescence microscopy to show that the Wip1 gene product p23 is a receptor binding protein. His-p23 also formed a stable complex with p24, a Wip1 protein of unknown function, suggesting that the latter is involved with p23 in host cell recognition. The narrow host range of phage Wip1 and the identification of p23 as a receptor binding protein offer a new range of suitable tools for the rapid identification of B. anthracis.     

Maintenance of Inbreeding Depression in a Highly Self-Fertilizing Tree, Magnolia obovata Thunb

Inbreeding depression is a major selective force that maintains outcrossing in flowering plants. If the long life and large mature size of trees cause high inbreeding depression via mitotic mutations and half-sib competition, these characteristics may increase inbreeding depression sufficiently to maintain traits that facilitate outcrossing even with high primary selfing rates (proportion of selfed ovules). Here, I report the maintenance of inbreeding depression in a population of a tree (Magnolia obovata Thunb.) with primary selfing rates greater than 0.8 resulting from geitonogamy. The progenies exhibited inbreeding depression for germination, seedling survival, and seedling mass (δ = 0.29–0.38), but no significant difference between crossing type in seedling height. Cumulative inbreeding depression for early survival (from zygote to 2-year-old stage) estimated from these results and from prior data on embryonic survival was high (δ_e = 0.91). The fixation index at maturity based on six allozyme loci was low (F_is = 0.08), indicating that significant inbreeding depression for late survival results in a low level of inbreeding with respect to gene transmission to the next generation. From these results, I estimated that inbreeding depression for late and lifetime survival equaled 0.69 and 0.97, respectively. These results suggest that M. obovata trees maintain high inbreeding depression at both early and late life stages, resulting in a low level of inbreeding despite a high primary selfing rate. The high inbreeding depression can be explained by previous theories and is consistent with the predicted maintenance of inbreeding depression in highly self-fertilizing tree populations. The inbreeding load due to the high primary selfing rate represents a cost of this tree’s pollination system for outcrossing, which is based on automimicry and mass flowering. Co-ordinating editor: S.-M. Chang     

High-throughput miRNA sequencing and identification of a novel ICE1-targeting miRNA in response to low temperature stress in Eucalyptus camaldulensis

• MicroRNAs (miRNAs) play a crucial role in the growth, development, morphogenesis, signal transduction, and stress response in plants. The ICE (Inducer of CBF expression)-CBF (C-repeat binding factor)-COR (Cold-regulated gene) regulatory cascade is an important signalling pathway in plant response to low temperature stress, and it remains unknown whether this pathway is regulated by miRNAs.
• In this study, high-throughput sequencing was employed for predicting and identifying the miRNAs that were likely to target the ICE-CBF-COR pathway in Eucalyptus camaldulensis. A novel ICE1-targeting miRNA, eca-novel-miR-259-5p (nov-miR259), was further analysed.
• A total of 392 conserved miRNAs and 97 novel miRNAs were predicted, including 80 differentially expressed miRNAs. Of these, 30 miRNAs were predicted to be associated with the ICE-CBF-COR pathway. The full-length of mature nov-miR259 was 22 bp and its precursor gene was 60 bp in length, with a typical hairpin structure. The RNA ligase-mediated 5′ amplification of cDNA ends (5′-RLM-RACE) and Agrobacterium-mediated tobacco transient expression assays demonstrated that nov-miR259 could cleave EcaICE1 in vivo. Moreover, qRT-PCR and Pearson's correlation analysis further revealed that the expression levels of nov-miR259 were almost significantly negatively correlated with those of its target gene, EcaICE1, and the other genes in the ICE-CBF-COR pathway.
• We first identified the nov-miR259 as a novel ICE1-targeting miRNA, and the nov-miR259-ICE1 module may be involved in regulating the cold stress response in E. camaldulensis.

     

Growth and yield functions for irrigated plantations of Eucalyptus camaldulensis in the hot desert of India

Eucalyptus camaldulensis forms a major portion of irrigated plantations in the hot desert of India and for effective management of these plantations, growth and yield functions are necessary. This paper describes the development of height, diameter and volume growth functions based on the analysis of the data collected from the permanent sample plots laid out in the study area. The Chapman-Richards equation could be used for the prediction of diameter growth while the Schumacher model could be considered for predicting volume growth. Some base-age variant and invariant site-index models, already reported in the literature, were compared in terms of relative accuracy and it was found that the Payandeh and Wang model performed the best among the four models tried.     

Identification of Scopoletin as a Phytoalexin of the Rubber Tree Hevea brasiliensis1

In leaves of Hevea sp. the production of a blue fluorescing phytoalexin is induced by various fungi. This compound is shown by chromatographic and spectrophotometric means to be scopoletin.     

Identification of Tropoelastin as a Ligand for the 65-kD FK506-binding Protein, FKBP65, in the Secretory Pathway

The folding and trafficking of tropoelastin is thought to be mediated by intracellular chaperones, although the identity and role of any tropoelastin chaperone remain to be determined. To identify proteins that are associated with tropoelastin intracellularly, bifunctional chemical cross-linkers were used to covalently stabilize interactions between tropoelastin and associated proteins in the secretory pathway in intact fetal bovine auricular chondrocytes. Immunoprecipitation of tropoelastin from cell lysates after cross-linking and analysis by SDS-PAGE showed the presence of two proteins of ~74 kD (p74) and 78 kD (p78) that coimmunoprecipitated with tropoelastin. Microsequencing of peptide fragments from a cyanogen bromide digest of p78 identified this protein as BiP and sequence analysis identified p74 as the peptidyl-prolyl cis–trans isomerase, FKPB65. The appearance of BiP and FKBP65 in the immunoprecipitations could be enhanced by the addition of brefeldin A (BFA) and N-acetyl-leu-leu-norleucinal (ALLN) to the culture medium for the final 4 h of labeling. Tropoelastin accumulates in the fused ER/Golgi compartment in the presence of BFA if its degradation is inhibited by ALLN (Davis, E.C., and R.P. Mecham. 1996. J. Biol. Chem. 271:3787–3794). The use of BFA and other secretion-disrupting agents suggests that the association of tropoelastin with FKBP65 occurs in the ER. Results from this study provide the first identification of a ligand for an FKBP in the secretory pathway and suggest that the prolyl cis–trans isomerase activity of FKBP65 may be important for the proper folding of the proline-rich tropoelastin molecule before secretion.     

Identification of nobiletin,a polymethoxyflavonoid,as an enhancer of adiponectin secretion

Adiponectin, an adipocyte-derived protein with insulin-sensitizing, anti-diabetic and anti-atherogenic activities, is known to be induced during adipocyte differentiation. Nobiletin, a citrus polymethoxy flavonoid, was found to induce the differentiation of ST-13 preadipocytes into mature adipocytes and enhance the production of adiponectin protein at a concentration of 10 μM.     

Emission of constitutive isoprene,induced monoterpenes,and other volatiles under high temperatures in Eucalyptus camaldulensis: A 13C labelling study

Eucalypts are major emitters of biogenic volatile organic compounds (BVOCs), especially volatile isoprenoids. Emissions and incorporation of ¹³C in BVOCs were measured in Eucalyptus camaldulensis branches exposed to rapid heat stress or progressive temperature increases, in order to detect both metabolic processes and their dynamics. Isoprene emission increased and photosynthesis decreased with temperatures rising from 30°C to 45°C, and an increasing percentage of unlabelled carbon was incorporated into isoprene in heat‐stressed leaves. Intramolecular labelling was also incomplete in isoprene emitted by heat‐stressed leaves, suggesting increasing contribution of respiratory (and possibly also photorespiratory) carbon. At temperature above 45°C, a drop of isoprene emission was mirrored by the appearance of unlabelled monoterpenes, green leaf volatiles, methanol, and ethanol, indicating that the emission of stored volatiles was mainly induced by cellular damage. Emission of partially labelled acetaldehyde was also observed at very high temperatures, suggesting a double source of carbon, with a large unlabelled component likely transported from roots and associated to the surge of transpiration at very high temperatures. Eucalypt plantations cover large areas worldwide, and our findings may dramatically change forecast and modelling of future BVOC emissions at planetary level, especially considering climate warming and frequent heat waves.