Mineral and Carbohydrate Nutrition of Plant Cell and Tissue Cultures

Recent advances in our understanding of the mineral (and carbohydrate) nutrition of cultured plant cells and tissues are reviewed. The methods used for empirical selection of nutrient composition of culture media for different plant genera/species and types of culture are critically evaluated.

The acquisition of nutrients is discussed in terms of their physical availability in the culture medium and uptake from the medium. The effect on uptake of factors such as pH and water potential and the relationship with growth rates and medium depletion are examined in detail.

Finally, some effects of nutrients on morphogenesis of plants are reviewed.     

Foliar water and solute absorption: an update

The absorption of water and solutes by plant leaves has been recognised since more than two centuries. Given the polar nature of water and solutes, the mechanisms of foliar uptake have been proposed to be similar for water and electrolytes, including nutrient solutions. Research efforts since the 19th century focussed on characterising the properties of cuticles and applying foliar sprays to crop plants as a tool for improving crop nutrition. This was accompanied by the development of hundreds of studies aimed at characterising the chemical and structural nature of plant cuticles from different species and the mechanisms of cuticular and, to a lower extent, stomatal penetration of water and solutes. The processes involved are complex and will be affected by multiple environmental, physico-chemical and physiological factors which are only partially clear to date. During the last decades, the body of evidence that water transport across leaf surfaces of native species may contribute to water balances (absorption and loss) at an ecosystem level has grown. Given the potential importance of foliar water absorption for many plant species and ecosystems as shown in recent studies, the aim of this review is to first integrate current knowledge on plant surface composition, structure, wettability and physico-chemical interactions with surface-deposited matter. The different mechanisms of foliar absorption of water and electrolytes and experimental procedures for tracing the uptake process are discussed before posing several outstanding questions which should be tackled in future studies.     

Methionine metabolism and multiple sclerosis

Context: Methylation reactions are particularly important in the brain and their inhibition can lead to a number of serious pathologies. Multiple sclerosis is one of the most common neurological disorders caused by interaction of genetic and environmental factors, but little is known about its cause or factors that contribute to the disorder. Although multiple sclerosis is primarily regarded as demyelinating disorder, there are no many articles focusing on methionine determination.

Objective: The aim of this work was to investigate whether serum methionine and its related compounds like homocysteine, cysteine, glutathione and asymmetric dimethylarginine were changed in multiple sclerosis patients.

Materials and methods: Sulphur-containing compounds were determined by using high-performance liquid chromatography with electrochemical detection in a single run for providing more complex view on methionine metabolism and asymmetric dimetylarginine was measured by a commercial enzyme-linked immunosorbent assay kit.

Results: Methionine and glutathione were decreased, but homocysteine, asymmetric dimethylarginine and cysteine were unchanged in patients with multiple sclerosis compared with controls.

Conclusions: Methionine and glutathione seem to be potential biomarkers for prognosis of the disease.     

Immuno-MALDI (iMALDI) mass spectrometry for the analysis of proteins in signaling pathways

Introduction: Biomarkers are commonly used to stratify cancer patients and guide targeted therapies, but most biomarkers are of a genomic nature. Discrepancies between the genome and proteome and the high rates of drug resistance indicate that proteomic analyses may provide additional critically important information. Here we present immuno-Matrix-Assisted Laser Desorption/Ionization (iMALDI), the combination of immuno-affinity enrichment of peptides followed by direct MALDI-mass spectrometry analysis. iMALDI is a highly sensitive, targeted protein-quantitation technique with the potential to measure clinically relevant signaling-pathway proteins using minimal sample amounts, thus improving upon existing methodologies.

Areas covered: We provide a brief overview of the current state of biomarker analysis technologies for modern cancer treatment. We also show the advantages of iMALDI for translating potential new biomarkers into the clinic, factors to consider for iMALDI assay development, and the utility of iMALDI for the quantitation of cell-signaling proteins.

Expert commentary: We see targeted mass spectrometry approaches such as iMALDI as an important part of improving patient responses to targeted therapies by providing highly sensitive, accurate, precise, and specific measurements of signaling-pathway proteins, both in tumor cells and in cells from the tumor microenvironment. iMALDI results can be integrated with other -omics data to aid in tumor-targeting therapies and immuno-oncology.     

Association between high-sensitivity cardiac troponin T and future cardiovascular incidence in a general Japanese population: results from the Tohoku medical megabank project

Purpose: Elevation of high-sensitivity cardiac troponin T (hs-cTnT) is associated with an increased risk of cardiovascular disease (CVD). This study determined whether hs-cTnT was detectable with N-terminal pro-b-type natriuretic peptide (NT-proBNP) and related to CV risk factors in a general Japanese population.

Materials and methods: The Tohoku Medical Megabank Organization pooled individual participant data for a population-based cohort study in the Iwate prefecture (n?=?30,193, age = 60.2?±?11.5?year).

Results: Hs-cTnT levels were higher in participants with hypertension, diabetes mellitus than in participants without these conditions (all ps < 0.001). Logistic regression analysis demonstrated that NT-proBNP was strongly associated with elevation of hs-cTnT (OR = 3.35, 95% CI = 2.90–3.89, p?<?0.001). The receiver operating characteristic curve analysis showed that hs-cTnT was one of useful biomarker for the differentiation of high risk for CVD (the Suita score ≥ 56) from a general population. Logistic regression analysis demonstrated hs-cTnT levels were related to the CVD high risk group (OR = 2.67, 95% CI = 2.28–3.14, p?<?0.001).

Conclusions: Hs-cTnT levels are associated with elevation of NT-proBNP and high Suita score, which suggests that elevated hs-cTnT is related to subclinical myocardial damage and indicates CV risk.     

Environment is more relevant than spatial structure as a driver of regional variation in tropical tree community richness and composition

Background: Understanding how factors related to environment and geographical distance explain community variation allows insights about how ecological niche and neutral processes control tropical community assembly.

Aims: Quantify how variation in regional tree community richness and composition in a humid tropical forest across a mountain chain are related to niche and putative neutral processes.

Methods: We used a variation partitioning routine based on Redundancy Analysis to model tropical tree community richness and composition within three distinct elevation belts, as a function of environment and spatial structure, using data from 32 studies in the Serra do Mar Range, south-eastern Brazil.

Results: Environmental effects were greater than spatial structure effects to explain community variation in the three elevation belts. There was a trend of decreasing spatial structure effects while environmental effects remained constant from lower to higher elevations. Patterns were congruent for species richness and composition.

Conclusions: We suggest that on tropical mountains, niche-related processes are equally relevant for tropical forest community assembly at all elevations, while neutral processes become weaker towards higher elevations. Determining if this trend is a consequence of the greater heterogeneity of environmental conditions associated with higher elevations in tropical mountainous terrain remains an important area of research.     

Flower colour variation in the montane plant Gentiana lutea L. (Gentianaceae) is unrelated to abiotic factors

Background: Flower colour variation among populations may result from the spatial variation of selective agents. The structure of phenotypic variation informs on the ecological processes related to this variation. Variation in floral traits is mainly attributed to variation in the pollinator fauna, while variation in vegetative traits is usually linked to abiotic factors or herbivores.

Aims: We investigated the geographical variation of flower colour (and correlated traits) in Gentiana lutea and the relationship with the variation in abiotic factors.

Methods: Phenotypic variation (flower colour, petal length, petal width, stalk length, leaf length, flower number, petal number and number of basal leaves) was assessed in 429 plants of 12 populations located at north-west Iberia. Additionally, we obtained data on the geographical coordinates, elevation, temperature, rainfall and radiation for each population.

Results: Populations mostly differed in flower colour, from orange to yellow from west to the east. Abiotic factors were unrelated to variation in either floral or vegetative traits.

Conclusions: Phenotypic variation among G. lutea populations does not result from adaptation to environmental factors. Other factors, such as historical events or selective pressure exerted by biotic interactions, might explain the flower colour variation in G. lutea along the Cantabrian Range.     

Mycorrhizal ecology on serpentine soils

Background: Serpentine ecosystems support different, often unique, plant communities; however, we know little about the soil organisms that associate with these ecosystems. Mycorrhizas, mutualistic symbioses between fungi and roots, are critical to nutrient cycling and energy exchange below ground.

Aims: We address three hypotheses: H1, diversity of mycorrhizal fungi in serpentine soils mirrors above-ground plant diversity; H2, the morphology of mycorrhizas and fungi on serpentine soils differs from that on non-serpentine; and H3, mycorrhizal fungal communities of the same or closely related hosts differ between serpentine and non-serpentine soils.

Methods: This review focuses on whether plant diversity on serpentine soils correlates with the below ground diversity of mycorrhizal fungi.

Results: Studies show that plants and fungi formed abundant ectomycorrhizal and arbuscular mycorrhizal symbioses on and off serpentine soils. No serpentine-endemic fungi were identified. Molecular analyses indicate distinct serpentine isolates for Cenococcum geophilum and for Acaulospora, suggesting adaptation to serpentine soils. While fungal sporocarp assemblages on serpentine sites resembled those off serpentine, fruiting of hypogeous fungi was greatly reduced.

Conclusions: Ectomycorrhizal fungal communities did not differ between soil types; however, arbuscular mycorrhizal communities differed in some cases but not others. The additive response to multiple factors, described as the serpentine syndrome, may explain part of the response by fungi.     

Apparent adult survival of the critically endangered Baltic Dunlin Calidris alpina schinzii during a period of strong population decline

Capsule: Apparent adult survival of the critically endangered Baltic Dunlin Calidris alpina schinzii, showed evidence of a decline between 1990 and 2006 from 0.817 to 0.650.

Aims: In Europe, declines in wet-grassland breeding waders have been attributed to changes in breeding habitat but long-term information on survival is rare. We examined whether adult survival of the Baltic Dunlin declined during a period of strong population decline.

Methods: We modelled apparent survival using Cormack–Jolly–Seber models and long-term capture–recapture data collected from a Danish population. We fitted models that constrained apparent adult survival with linear and quadratic trends, and compared them with constant and time dependent models to test whether survival declined during the study period.

Results: Models including linear and quadratic trends were most supported. However, the trend variables explained only 24–35% of observed temporal variance suggesting that a large portion of variation in survival remained undescribed. Model averaged estimates indicated a decline in adult survival from 0.817 to 0.650 between 1990 and 2006 with increased uncertainty towards the end.

Conclusion: Our results suggest that gradual long-term changes in adult survival may have contributed to the decline of the Baltic Dunlin.     

Development of an in vitro tumor spheroid culture model amenable to high-throughput testing of potential anticancer nanotherapeutics

Context: Three-dimensional tumor spheroid cultures are a better representative of in vivo solid tumors than monolayer cultures and should be used for testing potential nanotherapeutics in vitro.

Objective: To develop techniques to test the disposition and efficacy of nanocarrier formulations in spheroids in a cost-effective manner amenable to high-throughput testing.

Methods: Spheroids were obtained using a modified liquid overlay technique in a 96-well plate. Several nanocarrier formulations were prepared and tested in the spheroid model. The disposition of the formulations in the spheroids was determined by confocal microscopy while the effect of the drug-loaded formulations was assessed in terms of the cell viability, loss of membrane integrity, induction of caspases and inhibition of growth of the spheroids.

Results: The surface charge of the formulations influenced the accumulation of the nanocarrier and drug in the spheroid, with the cationic formulation accumulating to the greatest extent. Also, the smallest particle size formulation, micelles, penetrated to the greatest extent in the spheroid. The iRGD tumor-penetrating peptide co-administered with unmodified liposomes exhibited both high accumulation and penetration. The effect studies revealed that the formulations that penetrated or accumulated to the highest extent in the spheroid exhibited better antitumor activity compared to the other formulations.

Conclusion: The 96-well plate format spheroid model developed in the study can be used toward the rational selection of nanocarrier therapeutics prior to their testing in in vivo models.     

Methodological approaches and insights on protein aggregation in biological systems

Introduction: The proper folding of native proteins is critical and dynamic, but inherently unstable. Therefore, proteins eventually end up adopting misfolded conformations which compromise their function and may even trigger aggregation. Risk factors for neurodegenerative, metabolic and heart diseases compromise cellular protein quality-control systems, promoting protein aggregation. Multiple protein post-translational modifications dynamically regulate protein aggregation and disaggregation in a very complex, intricate and delicate balance.

Areas covered: Herein, we overview the more promising techniques and approaches for the elucidation of the biological implications of protein aggregation. The particular insights provided by different techniques were discriminated and several examples of post-translational modifications together with their targets were pooled and critically discussed, representing promising future therapeutic targets.

Expert commentary: In the years to come, differences between physiological and pathological protein aggregation will certainly become easier to determine. Techniques such as hydrogen/deuterium exchange, circular dichroism spectroscopy and novel mass spectrometry-based approaches are being optimized and are expected to introduce inhibitors of protein aggregation into the clinic. However, protein aggregation is not an isolated phenomenon, but rather influenced by multiple cellular components which complete knowledge is still far.     

The relationship of single-strand breaks in DNA to breast cancer risk and to tissue concentrations of oestrogens

Context: Clinical study of breast cancer patients in Chicago, IL, USA.

Objective: Ascertain the utility of measurements of single-strand breaks (SSB) in DNA for assessment of breast cancer risk.

Methods: Fine-needle aspirates of the breast, SSB by nick translation, percent breast density (PBD), Gail model risk, cumulative methylation index (CMI), enzymes of DNA repair and tissue antioxidants.

Results: DNA repair enzymes and 4-hydroxyestradiol were negatively associated with SSB; CMI and PBD were positively associated.

Conclusions: Quantitative measurement of SSBs by this procedure indicates the relative number of SSBs and is related to promoter methylation, antioxidant availability and percent breast density.     

Circulating levels of apoptotic markers and oxidative stress parameters in women with polycystic ovary syndrome: a case-controlled descriptive study

Context: Apoptotic dysregulation plays a role in the pathogenesis of polycystic ovary syndrome (PCOS).

Objective: To evaluate circulatory apoptotic markers and oxidative stress in patients with PCOS.

Materials and methods: Forty-four women with PCOS, and 44 healthy women as controls were enrolled in the study. Oxidative stress parameters and caspases levels were measured in serum.

Results: The caspase 9 level was significantly lower and related with oxidant status in patients with PCOS, while the circulating levels of caspases 3 and 7 were statistically similar in both groups.

Discussion: This study is the first report demonstrating the circulating levels of apoptotic markers and their relationship with oxidant status in PCOS.

Conclusion: The circulating caspase 9 and oxidant status might contribute to apoptotic dysregulation in PCOS.     

Development of quantitative mass spectrometric immunoassay for serum amyloid A

Objective: Proteins can exist as multiple proteoforms in vivo that can have important roles in physiological and pathological states.

Methods: We present the development and characterization of mass spectrometric immunoassay (MSIA) for quantitative determination of serum amyloid A (SAA) proteoforms.

Results: Intra- and inter-day precision revealed CVs <10%. Against existing SAA ELISA, the developed MSIA showed good correlation according to the Altman–Bland plot. Individual concentrations of the SAA proteoforms across a cohort of 170 samples revealed 7 diverse SAA polymorphic types and 12 different proteoforms.

Conclusion: The new SAA MSIA enables parallel analysis of SAA polymorphisms and quantification of all expressed SAA proteoforms, in a high-throughput and time-efficient manner.     

The macroecology of animal versus wind pollination: ecological factors are more important than historical climate stability

Background: The relative frequency of wind- and animal-pollinated plants a non-randomly distributed across the globe and numerous hypotheses have been raised for the greater occurrence of wind pollination in some habitats and towards higher latitudes. To date, however, there has been no comprehensive global investigation of these hypotheses.

Aims: Investigating a range of hypotheses for the role of biotic and abiotic factors as determinants of the global variation in animal vs. wind pollination.

Methods: We analysed 67 plant communities ranging from 70º north to 34º south. For these we determined habitat type, species richness, insularity, topographic heterogeneity, current climate and late-quaternary climate change. The predictive effects of these factors on the proportion of wind- and animal-pollinated plants were tested using correlations, ordinary least squares (OLS) and logistic regression analyses with information-theoretic model selection.

Results: The proportion of animal-pollinated plant species was positively associated with plant species richness and current temperature. Furthermore, in forest, animal pollination was positively related to precipitation. Historical climate was only weakly and idiosyncratically correlated with animal pollination.

Conclusion: Results were consistent with the hypothesised reduced chance for wind-transported pollen reaching conspecific flowers in species-rich communities, fewer constraints on nectar production in warm and wet habitats, and reduced relative effectiveness of wind dispersal in humid areas. There was little evidence of a legacy of historical climate change affecting these patterns.     

Broad environmental tolerance of native root-nodule bacteria of Biserrula pelecinus indicate potential for soil fertility restoration

Background: Biserrula pelecinus is an annual legume native to the Mediterranean basin, found in pastureland, alone or in association with other legumes (Leguminosae) and grasses (Poaceae). It has been used in revegetation programmes of mining wastes showing phytoremediation potentials and thus becoming potentially highly attractive for plant ecology and restoration management of natural ecosystems.

Aims: To characterise native root-nodule bacteria isolated from B. pelecinus from the Iberian Peninsula, and to select suitable N fixers for field-application and soil rehabilitation.

Methods: Strains were isolated and molecularly identified by 16S rRNA amplification and sequencing. Strains were phenotypically characterised in different abiotic conditions (acidity, salinity and heavy metals) and tested for their ability to fix atmospheric N₂. The most suitable N fixers were applied in greenhouse experiments with B. pelecinus under different fertilization levels to assess their tolerance to fertilized and polluted soils, commonly encountered in restoration projects.

Results: B. pelecinus root-nodule isolates tolerated pH from 4.5 to 9.5 grew in saline conditions (2.5% of NaCl), and tolerated 50 µM of Al³⁺ and Mn²⁺. Three isolates efficient in N₂ fixation, relative to the reference Mesorhizobium strain, were considered excellent candidates for the amelioration of nutrient poor sites.

Conclusions: These results provide valuable information for the potential use in soil restoration of B. pelecinus in a wide-range of conditions, exploiting the natural variability of its root-nodule bacteria.     

Mapping the human skeletal muscle proteome: progress and potential

Introduction: Human skeletal muscle represents 40% of our body mass and deciphering its proteome composition to further understand mechanisms regulating muscle function under physiological and pathological conditions has proved a challenge. The inter-individual variability, the presence of structurally and functionally different muscle types and the high protein dynamic range require carefully selected methodologies for the assessment of the muscle proteome. Furthermore, physiological studies are understandingly hampered by ethical issues related to biopsies on healthy subjects, making it difficult to recruit matched controls essential for comparative studies.

Areas covered: This review critically analyses studies performed on muscle to date and identifies what still remains unknown or poorly investigated in physiological and pathological states, such as training, aging, metabolic disorders and muscular dystrophies.

Expert commentary: Efforts should be made on biological fluid analyses targeting low abundant/low molecular weight fragments generated from muscle cell disruption to improve diagnosis and clinical monitoring. From a methodological point of view, particular attention should be paid to improve the characterization of intact proteins and unknown post translational modifications to better understand the molecular mechanisms of muscle disorders.     

A Review of Thermotherapy to Free Plant Materials from Pathogens,Especially Seeds from Bacteria

Treating planting materials with heat is a one-century-old method of disease control that has proved to be efficient against various pathogenic microorganisms. Thermotherapy, simple in principle, consists in heat treatment of plant parts at temperature/time regimes that kill the conserved pathogen and that are only slightly injurious to the host. Heat is applied mainly by water, air, or vapor.

A large variety of plant parts can be heat treated: Whole tree, scions, vitroplants, seedlings, stalks, cuttings, sprouts, cut flowers, seeds, bulbs, tubers, corms, or fruit and vegetables in storage. The target pathogenic microorganisms are mainly fungi, viruses, and bacteria. Many studies show the success of reducing diseases by heat. Thermotherapy also is the main means, associated with meristem and tip culture, of producing virus-free explants from infected mother-plants.

Most bacterial diseases of annual plants are seed-borne. Seed-transmission provides numerous foci of primary infection in the field and only a relatively small amount of infested seeds is sufficient to promote serious disease outbreaks. To disinfect seeds, authors mainly use hot water and hot air treatments. Satisfactory control has been obtained for several bacterial diseases (on tomato, tobacco, rice, barley, cucumber, Crucifers, pumpkin, guar, and cotton), mostly caused by the genera Xanthomonas and Pseudomonas. Thermotherapy is more difficult to use with large seeds of legumes, such as pea, bean, or soybean, because a significant decrease of germination is often obtained before the bacteria have been totally killed. The success of thermotherapy may be improved by combination with chemicals at the seed stage, by sprays during plant growth, or by replacing water with nonaqueous fluids.

When no efficient chemicals are known to control a disease, treating seeds by heat may be of great interest. However, the method requires studies to determine the most appropriate kind of heat for a particular plant part, and the optimal combination of time and temperature of exposure to use for the best efficiency with the least damage to the host.     

Fruit production along roads and footpaths in an Atlantic rain forest area

Background: Pathways (footpaths and roads) in forests are associated with edge effects, affecting forest structure and composition and associated wildlife. However, little is known about how edge effects along pathways may impact the dynamics of fruit production and their availability for frugivores.

Aim: We related pathway width as a proxy for edge effects to fruit production. Our underlying hypothesis was that pathway width would be positively related to fruit production.

Methods: We observed fruit production along three pathways of different widths – 2, 10 and 20 m wide – and in a control area of undisturbed forest in an Atlantic rain forest stand monthly over a 2-year period.

Results: The number of species and individuals-bearing fruit was higher along the wider pathways than along the narrowest pathway and in the control area. The amount of zoochorous fruits was higher in the control area than along pathways, and the widest pathway had higher non-zoochorous fruits production. Fruiting peaks occurred along pathways, while fruiting in the control area was aseasonal.

Conclusions: Pathway width is related to fruit type and its quantity and temporal availability. These effects extend towards the forest interior beyond 35 m. The presence of paths affects food resources for frugivores and thus can contribute to reconfiguring the spatio-temporal distribution of the fauna.