Salinity stress constrains photosynthesis in Fraxinus ornus more when growing in partial shading than in full sunlight: consequences for the antioxidant defence system

Background and Aims

A major challenge in plant ecophysiology is understanding the effects of multiple sub-optimal environmental conditions on plant performance. In most Mediterranean areas soil salinity builds up during the summer because of low availability of soil water coupled with hot temperatures. Although sunlight and soil salinity may strongly interact in determining a plant''s performance, this has received relatively little attention.

Methods

Two-year-old seedlings of Fraxinus ornus were grown outdoors in pots during a Mediterranean summer in either 45 % (shaded plants) or 100 % (sun plants) sunlight irradiance and were supplied with either deionized water or deionized water plus 75 mm NaCl. Morpho-anatomical traits, water and ionic relations, gas exchange and photosystem II performance, concentrations of individual carotenoids, activity of antioxidant enzymes, concentrations of ascorbic acid and individual polyphenols were measured in leaves. Leaf oxidative stress and damage were estimated by in vivo analysis of stable free radicals and ultrastructural analyses.

Key Results

Leaf concentrations of potentially toxic ions did not markedly differ in shaded or sun plants in response to salinity. Leaves of sun plants displayed superior water use efficiency compared with leaves of shaded plants, irrespective of salinity treatment, and had both better stomatal control and higher CO₂ carboxylation efficiency than leaves of shaded plants. In the salt-treated groups, the adverse effects of excess midday irradiance were greater in shade than in sun plants. The activity of enzymes responsible for detoxifying hydrogen peroxide decreased in shaded plants and increased in sun plants as a result of salinity stress. In contrast, the activity of guaiacol peroxidase and the concentration of phenylpropanoids increased steeply in response to salinity in shaded plants but were unaffected in sun plants.

Conclusions

It is concluded that salinity may constrain the performance of plants growing under partial shading more severely than that of plants growing under full sun during summer. The results suggest co-ordination within the antioxidant defence network aimed at detoxifying salt-induced generation of reactive oxygen species.     

Species’ traits influence ground beetle responses to farm and landscape level agricultural intensification in Europe

Agricultural intensification may result in important shifts in insect community composition and function, but this remains poorly explored. Studying how groups of species with shared traits respond to local and landscape scale land-use management can reveal mechanisms behind such observed impacts. We tested if ground beetles (Coleoptera: Carabidae) divided into trait groups based on body sizes, wing morphologies and dietary preferences respond differently to farming practise (organic and conventional), farming intensity (measured as yield) and landscape complexity (measured as the proportion of arable land within a 1,000 m radius) across Europe. We used data from 143 farms in five regions in northern and central Europe. Organic farms did not differ in abundance or richness of any trait group compared to conventional farms. As farm scale intensity (yield) increased, overall abundance of beetles decreased, but abundances of small and medium sized beetles, as well as that of wingless beetles, were unaffected. Overall species richness was not affected by yield, whereas consideration of traits revealed that phytophagous and omnivorous beetles were less species rich on farms with high yields. Increasing the proportion of arable land in the landscape increased overall beetle abundance. This was driven by an increase in omnivorous beetles. The total species richness was not affected by an increase in the proportion arable land, although the richness of wingless beetles was found to increase. Potential effects on ecosystem functioning need to be taken into account when designing schemes to maintain agricultural biodiversity, because species with different ecological traits respond differently to local management and landscape changes.     

Compartment differences of inflammatory activity in chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is associated with local and systemic inflammation. The knowledge of interaction and co-variation of the inflammatory responses in different compartments is meagre.

Method

Healthy controls (n = 23), smokers with (n = 28) and without (n = 29) COPD performed spirometry and dental examinations. Saliva, induced sputum, bronchoalveolar lavage (BAL) fluid and serum were collected. Inflammatory markers were assessed in all compartments using ELISA, flow cytometry and RT-PCR.

Results

Negative correlations between lung function and saliva IL-8 and matrix metalloproteinase-9 (MMP-9) were found in smokers with COPD. IL-8 and MMP-9 in saliva correlated positively with periodontal disease as assessed by gingival bleeding in non-smokers.Tumor necrosis factor-α (TNF-α) in saliva, serum and TNF-α mRNA expression on macrophages in BAL-fluid were lower in smokers than in non-smokers. There were positive correlations between soluble TNF-α receptor 1 (sTNFR1) and soluble TNF-α receptor 2 (sTNFR2) in sputum, BAL-fluid and serum in all groups. Sputum interleukin-8 (IL-8) or interleukin-6 (IL-6) was positively correlated with sTNFR1 or sTNFR2 in non-smokers and with sTNFR2 in COPD.

Conclusion

Saliva which is convenient to collect and analyse, may be suitable for biomarker assessment of disease activity in COPD. An attenuated TNF-α expression was demonstrated by both protein and mRNA analyses in different compartments suggesting that TNF-α response is altered in moderate and severe COPD. Shedding of TNFR1 or TNFR2 is similarly regulated irrespective of airflow limitation.     

Isolation of β-globin-related genes from a human cosmid library

A human gene library was constructed using an improved cloning technique for cosmid vectors. Human placental DNA was partially digested with restriction endonuclease Mboi, size-fractionated and ligated to BamHI-cut and phosphatase-treated cosmid vector pJB8. After packaging in λ phage particles, the recombinant DNA was transduced into Escherichia coli 1400 or HB101 followed by selection on ampicillin for recombinant E. coli. 150000 recombinant-DNA-containing colonies were screened for the presence of the human β-globin related genes. Five recombinants were isolated containing the human β-globin locus and encompassing approx. 70 kb of human DNA.     

The Genome of Thermosipho africanus TCF52B: Lateral Genetic Connections to the Firmicutes and Archaea

Lateral gene transfers (LGT) (also called horizontal gene transfers) have been a major force shaping the Thermosipho africanus TCF52B genome, whose sequence we describe here. Firmicutes emerge as the principal LGT partner. Twenty-six percent of phylogenetic trees suggest LGT with this group, while 13% of the open reading frames indicate LGT with Archaea.Thermosipho africanus TCF52B was isolated from produced fluids of a high-temperature oil reservoir in the North Sea using fish waste as the only substrate (4). Phylogenetic analyses based on the 16S rRNA gene sequence and DNA-DNA hybridization placed it as a strain of Thermosipho africanus, which was first isolated from a shallow marine hydrothermal system in Djibouti, Africa (8, 21).The complete genome sequence of this strain was determined by the conventional whole-genome shotgun strategy. Genomic libraries containing 1- to 4-kb and 40-kb fragments were constructed, and sequence chromatograms were produced using a MegaBACE 1000 capillary DNA sequencer (GE Healthcare). Nucleotide skews were computed as described previously (11). Automated open reading frame (ORF) identification and annotation were performed using the annotation software Manatee made available by TIGR (23). Pseudogenes were identified by doing BLAST searches of neighboring ORFs with the same or similar annotations and by using the program Psi-phi (9, 10), and clustered regularly interspaced short palindromic repeat loci (CRISPRs) were identified using the web site http://crispr.u-psud.fr/crispr/CRISPRHomePage.php with the default parameters (6). Maximum-likelihood (ML) trees (WAG [Γ+Ι model, four categories]) were constructed from protein-coding ORFs using PHYML and the PhyloGenie package (5). Recently, several Thermotogales genomes have become available in GenBank. As these genomes had not been published yet, we did not include them in any “genome-scale” analyses (i.e., the phylogenetic analyses). We did, however, include them in the BLAST analyses of mobile Thermosipho africanus genes.The genome of Thermosipho africanus strain TCF52B is a single circular chromosome consisting of 2,016,657 bp with an average G+C content of 30.8%. Strand asymmetries, such as GC skew and tetramer skews, are pronounced and show two clear singularity points, located at roughly 8 kb and 1033 kb from the +1 site (see Fig. S1 in the supplemental material). Since these two points are diametrically opposed on the circular chromosome, dividing it into two halves with opposite compositional skews, they make good candidates for the putative origin and termination of replication. The 1,033-kb region is likely to harbor the origin, since GC skew becomes positive past this location, as in most bacterial genomes with a known origin.The genome contains 2,000 potential coding sequences, of which 1913 are putative protein-coding ORFs, 30 are putatively assigned as pseudogenes, and 57 encode RNA. A comparison to the genome of Thermotoga maritima is given in Table ​Table1.1. The Thermosipho africanus genome is about 156 kb larger than the Thermotoga maritima genome and carries 36 more ORFs. The genome contains duplicated regions comprising paralogous gene copies, CRISPRs, and mobile genetic elements, which collectively provide considerable indirect evidence for genomic instability and acquisition of exogenous genetic information.

TABLE 1.

General features of the Thermosipho africanus genome, with a comparison to Thermotoga maritima

Measuring mitochondrial and cytoplasmic Ca2+ in EGFP expressing cells with a low-affinity Calcium Ruby and its dextran conjugate

The limited choice and poor performance of red-emitting calcium (Ca²⁺) indicators have hampered microfluorometric measurements of the intracellular free Ca²⁺ concentration in cells expressing yellow- or green-fluorescent protein constructs. A long-wavelength Ca²⁺ indicator would also permit a better discrimination against cellular autofluorescence than the commonly used fluorescein-based probes. Here, we report an improved synthesis and characterization of Calcium Ruby, a red-emitting probe consisting of an extended rhodamine chromophore (578/602 nm peak excitation/emission) conjugated to BAPTA and having an additional NH₂ linker arm. The low-affinity variant (K_D,Ca ～30 μM) with a chloride in meta position that was specifically designed for the detection of large and rapid Ca²⁺ transients. While Calcium Ruby is a mitochondrial Ca²⁺probe, its conjugation, via the NH₂ tail, to a 10,000 MW dextran abolishes the sub-cellular compartmentalization and generates a cytosolic Ca²⁺ probe with an affinity matched to microdomain Ca²⁺ signals. As an example, we show depolarization-evoked Ca²⁺ signals triggering the exocytosis of individual chromaffin granules. Calcium Ruby should be of use in a wide range of applications involving dual- or triple labeling schemes or targeted sub-cellular Ca²⁺ measurements.     

A permeant regulating its permeation pore: inhibition of pannexin 1 channels by ATP

Pannexin 1 forms a large membrane channel that, based on its biophysical properties and its expression pattern, is a prime candidate to represent an ATP release channel. Pannexin 1 channel activity is potentially deleterious for cells as indicated by its involvement in the P2X7 death complex. Here we describe a negative feedback loop controlling pannexin 1 channel activity. ATP, permeant to pannexin 1 channels, was found to inhibit its permeation pathway when applied extracellularly to oocytes expressing pannexin 1 exogenously. ATP analogues, including benzoylbenzoyl-ATP, suramin, and brilliant blue G were even more effective inhibitors of pannexin 1 currents than ATP. These compounds also attenuated the uptake of dyes by erythrocytes, which express pannexin 1. The rank order of the compounds in attenuation of pannexin 1 currents was similar to their binding affinities to the P2X7 receptor, except that receptor agonists and antagonists both were inhibitory to the channel. Mutational analysis identified R75 in pannexin 1 to be critical for ATP inhibition of pannexin 1 currents.     

Different Lepidopteran Elicitors Account for Cross-Talk in Herbivory-Induced Phytohormone Signaling

Salicylic acid (SA), jasmonic acid (JA), ethylene (ET), and their interactions mediate plant responses to pathogen and herbivore attack. JA-SA and JA-ET cross-signaling are well studied, but little is known about SA-ET cross-signaling in plant-herbivore interactions. When the specialist herbivore tobacco hornworm (Manduca sexta) attacks Nicotiana attenuata, rapid and transient JA and ET bursts are elicited without significantly altering wound-induced SA levels. In contrast, attack from the generalist beet armyworm (Spodoptera exigua) results in comparatively lower JA and ET bursts, but amplified SA bursts. These phytohormone responses are mimicked when the species' larval oral secretions (OS_Se and OS_Ms) are added to puncture wounds. Fatty acid-amino acid conjugates elicit the JA and ET bursts, but not the SA burst. OS_Se had enhanced glucose oxidase activity (but not β-glucosidase activity), which was sufficient to elicit the SA burst and attenuate the JA and ET levels. It is known that SA antagonizes JA; glucose oxidase activity and associated hydrogen peroxide also antagonizes the ET burst. We examined the OS_Ms-elicited SA burst in plants impaired in their ability to elicit JA (antisense [as]-lox3) and ET (inverted repeat [ir]-aco) bursts and perceive ET (35s-etr1b) after fatty acid-amino acid conjugate elicitation, which revealed that both ET and JA bursts antagonize the SA burst. Treating wild-type plants with ethephone and 1-methylcyclopropane confirmed these results and demonstrated the central role of the ET burst in suppressing the OS_Ms-elicited SA burst. By suppressing the SA burst, the ET burst likely facilitates unfettered JA-mediated defense activation in response to herbivores that otherwise would elicit SA.