How do vascular plants perform photosynthesis in extreme environments? An integrative ecophysiological and biochemical story

In this work, we review the physiological and molecular mechanisms that allow vascular plants to perform photosynthesis in extreme environments, such as deserts, polar and alpine ecosystems. Specifically, we discuss the morpho/anatomical, photochemical and metabolic adaptive processes that enable a positive carbon balance in photosynthetic tissues under extreme temperatures and/or severe water‐limiting conditions in C₃ species. Nevertheless, only a few studies have described the in situ functioning of photoprotection in plants from extreme environments, given the intrinsic difficulties of fieldwork in remote places. However, they cover a substantial geographical and functional range, which allowed us to describe some general trends. In general, photoprotection relies on the same mechanisms as those operating in the remaining plant species, ranging from enhanced morphological photoprotection to increased scavenging of oxidative products such as reactive oxygen species. Much less information is available about the main physiological and biochemical drivers of photosynthesis: stomatal conductance (g_s), mesophyll conductance (g_m) and carbon fixation, mostly driven by RuBisCO carboxylation. Extreme environments shape adaptations in structures, such as cell wall and membrane composition, the concentration and activation state of Calvin–Benson cycle enzymes, and RuBisCO evolution, optimizing kinetic traits to ensure functionality. Altogether, these species display a combination of rearrangements, from the whole‐plant level to the molecular scale, to sustain a positive carbon balance in some of the most hostile environments on Earth.     

Impact of the non-indigenous shrub species Spartium junceum (Fabaceae) on native vegetation in central Spain

Aims The introduction of potentially invasive species through ornamental cultivation or for rehabilitation purposes is a serious environmental problem. They cause damage to biodiversity through loss, increased mortality or ' in situ ' selection phenomena in natural flora. Spartium junceum is a Mediterranean shrub that is not native in most areas of the Iberian Peninsula, although it is extensively grown for the rehabilitation of roadsides. We have investigated the effect on the native vegetation of an old S. junceum (Fabaceae) plantation in a conservation area in the centre of the Iberian Peninsula: the Cuenca Alta del Manzanares nature reserve in Madrid.Methods We compared S. junceum stands with the native nanophanerophytic Cistus ladanifer community at different ecosystem properties: soil properties, temporal soil seed bank contents, standing vegetation and net primary production of annual grasslands growing in these shrublands.Important findings The results highlighted S. junceum 's ability to become established in the new environment (marginal areas of the nature reserve) and ensure its successful growth. This is more apparent in northern and eastern exposures where this formation contacts with the core of the best conserved native vegetation in the nature reserve. Soils under Spartium showed a higher nitrogen content, indicating its capacity—in common with other legumes—to fix N, and conferring an advantage over Cistus, which is N-limited. Other soil nutrients such as phosphorus, magnesium and calcium and water availability are also higher in Spartium soils than in Cistus. Phosphorus is usually a constraint for N-fixers, but in our study, it is the most significant soil variable in both shrub formations and is important to the success of Spartium. Water availability is a key factor for Mediterranean vegetation, and particularly in autumn when soils are recharged. The Spartium formation is able to retain water as its growth produces a closer canopy than Cistus, thereby preventing water evaporation and contributing to the success of this species. Perennials are more frequent in the standing vegetation than in the seed bank, whereas therophytes are similar. The standing vegetation has therophytes and chamaephytes as the predominant growth forms in Spartium sites, and hemicryptophytes and phanerophytes in Cistus. Therophytes are dominant in Spartium and Cistus seed banks, although the first formation has more species. Spartium has a higher number of hemicryptophytes and Cistus is higher in phanerophytes. Northern and eastern aspects show significant differences in richness—with a predominance of annual weed species in Spartium —and in above-ground net primary production, probably as a consequence of the nutrients present in the soils. Ruderal annual species under Spartium (Bromus tectorum, Chenopodium album) have higher germination rates in the greenhouse than in the standing vegetation, suggesting they are at potential risk if environmental conditions change.     

Mitochondrial DNA haplogroups and risk of new-onset diabetes among tacrolimus-treated renal transplanted patients

Background and aims

Tacrolimus (Tac) is an immunosuppressive drug widely used to avoid organ rejection. New-onset diabetes after transplantation (NODAT) is a major complication among transplanted patients who receive Tac. The increased risk for NODAT could be partly mediated by the effect of Tac on mitochondria from pancreatic beta-cells. Common and rare mitochondrial DNA variants have been linked to the risk of diabetes. Our aim was to determine whether mtDNA polymorphisms/haplogroups were associated with NODAT in Tac-treated kidney transplanted.

Methods

Seven polymorphisms that define the common European haplogroups were determined in 115 NODAT and 197 no-NODAT patients.

Results

Haplogroup H was significantly more frequent in the NODAT group (50% vs. 35%; p = 0.01, OR = 1.82). There was no difference between patients without and with (n = 106) D2M prior to the transplant.

Conclusions

Mitochondrial haplogroup H was associated with the risk for NODAT among Tac-treated transplanted patients. The reported differences between the mtDNA variants could explain the increased NODAT-risk among H-patients.     

Mycobacterium tuberculosis Multidrug Resistant Strain M Induces an Altered Activation of Cytotoxic CD8+ T Cells

In human tuberculosis (TB), CD8⁺ T cells contribute to host defense by the release of Th1 cytokines and the direct killing of Mycobacterium tuberculosis (Mtb)-infected macrophages via granule exocytosis pathway or the engagement of receptors on target cells. Previously we demonstrated that strain M, the most prevalent multidrug-resistant (MDR) Mtb strain in Argentine, is a weak inducer of IFN-γ and elicits a remarkably low CD8-dependent cytotoxic T cell activity (CTL). In contrast, the closely related strain 410, which caused a unique case of MDR-TB, elicits a CTL response similar to H37Rv. In this work we extend our previous study investigating some parameters that can account for this discrepancy. We evaluated the expressions of the lytic molecules perforin, granzyme B and granulysin and the chemokine CCL5 in CD8⁺ T cells as well as activation markers CD69 and CD25 and IL-2 expression in CD4⁺ and CD8⁺ T cells stimulated with strains H37Rv, M and 410. Our results demonstrate that M-stimulated CD8⁺ T cells from purified protein derivative positive healthy donors show low intracellular expression of perforin, granzyme B, granulysin and CCL5 together with an impaired ability to form conjugates with autologous M-pulsed macrophages. Besides, M induces low CD69 and IL-2 expression in CD4⁺ and CD8⁺ T cells, being CD69 and IL-2 expression closely associated. Furthermore, IL-2 addition enhanced perforin and granulysin expression as well as the degranulation marker CD107 in M-stimulated CD8⁺ T cells, making no differences with cells stimulated with strains H37Rv or 410. Thus, our results highlight the role of IL-2 in M-induced CTL activity that drives the proper activation of CD8⁺ T cells as well as CD4⁺ T cells collaboration.     

Characterization of Bacterial,Archaeal and Eukaryote Symbionts from Antarctic Sponges Reveals a High Diversity at a Three-Domain Level and a Particular Signature for This Ecosystem

Sponge-associated microbial communities include members from the three domains of life. In the case of bacteria, they are diverse, host specific and different from the surrounding seawater. However, little is known about the diversity and specificity of Eukarya and Archaea living in association with marine sponges. This knowledge gap is even greater regarding sponges from regions other than temperate and tropical environments. In Antarctica, marine sponges are abundant and important members of the benthos, structuring the Antarctic marine ecosystem. In this study, we used high throughput ribosomal gene sequencing to investigate the three-domain diversity and community composition from eight different Antarctic sponges. Taxonomic identification reveals that they belong to families Acarnidae, Chalinidae, Hymedesmiidae, Hymeniacidonidae, Leucettidae, Microcionidae, and Myxillidae. Our study indicates that there are different diversity and similarity patterns between bacterial/archaeal and eukaryote microbial symbionts from these Antarctic marine sponges, indicating inherent differences in how organisms from different domains establish symbiotic relationships. In general, when considering diversity indices and number of phyla detected, sponge-associated communities are more diverse than the planktonic communities. We conclude that three-domain microbial communities from Antarctic sponges are different from surrounding planktonic communities, expanding previous observations for Bacteria and including the Antarctic environment. Furthermore, we reveal differences in the composition of the sponge associated bacterial assemblages between Antarctic and tropical-temperate environments and the presence of a highly complex microbial eukaryote community, suggesting a particular signature for Antarctic sponges, different to that reported from other ecosystems.     

Proton leak modulation in testicular mitochondria affects reactive oxygen species production and lipid peroxidation

Mitochondrial proton leak can account for almost 20% of oxygen consumption and it is generally accepted that this process contributes to basal metabolism. In order to clarify the role of basal proton leak in testicular mitochondria, we performed a comparative study with kidney and liver mitochondrial fractions. Proton leak stimulated by linoleic acid and inhibited by guanosine diphosphate (GDP) was detected, in a manner that was correlated with protein levels for uncoupling protein 2 (UCP2) in the three fractions. Modulation of proton leak had an effect on reactive oxygen species production as well as on lipid peroxidation, and this effect was also tissue‐dependent. However, a possible role for the adenine nucleotide transporter (ANT) in testicular mitochondria proton leak could not be excluded. The modulation of proton leak appears as a possible and attractive target to control oxidative stress with implications for male gametogenesis. Copyright © 2010 John Wiley & Sons, Ltd.     

Membrane-transferring sequences of the HIV-1 Gp41 ectodomain assemble into an immunogenic complex

The membrane-proximal stem region of gp41 has been postulated to host the two conserved membrane-transferring domains that promote HIV-1 fusion: the amino-terminal fusion peptide (FP) and the highly aromatic pre-transmembrane sequence. Our results confirm that the hydrophobic FP and membrane-proximal sequences come into contact and form structurally defined complexes. These complexes are immunogenic and evoke responses in rabbits that compete with the recognition of native functional gp41 by the 2F5 monoclonal antibody. We conclude that co-assembly of the FP and the pre-transmembrane sequences might exert a constraint that helps maintain a gp41 stem region pre-fusion structure.     

Attraction of Fruit-Eating Bats with Essential Oils of Fruits: A Potential Tool for Forest Restoration

Previous tests with essential oils from ripe chiropterochoric fruits suggested they can be used to attract and capture fruit-eating bats inside forest remnants. Here we evaluated the efficiency of these oils to attract frugivorous bats to open areas. We performed field tests with artificial fruits impregnated with essential oils of the genera Piper or Ficus that were attached to two groups of mist-nets set 50 m outside the border of a forest remnant. One group of artificial fruits received the corresponding oil isolated through hydrodistillation and the other received water only. Fruits with oils attracted significantly more fruit-eating bats, especially Artibeus lituratus that regularly crosses open habitats to reach other forest remnants. The highly significant attraction of A. lituratus by the oil of Piper was unexpected, since this bat is a specialist on Ficus fruits. We hypothesize that in habitats with no fruit available it is possible to attract frugivorous bats with the odor of several ripe fruit species. Furthermore, we verified that almost half of the individuals captured defecated seeds, indicating that the oils also attract recently fed bats, even when their preferred food is available nearby. This technique potentially may increase seed rain at specific locations, being particularly promising to restoration projects.     

Comparative High-Density Microarray Analysis of Gene Expression during Growth of Lactobacillus helveticus in Milk versus Rich Culture Medium

Lactobacillus helveticus CNRZ32 is used by the dairy industry to modulate cheese flavor. The compilation of a draft genome sequence for this strain allowed us to identify and completely sequence 168 genes potentially important for the growth of this organism in milk or for cheese flavor development. The primary aim of this study was to investigate the expression of these genes during growth in milk and MRS medium by using microarrays. Oligonucleotide probes against each of the completely sequenced genes were compiled on maskless photolithography-based DNA microarrays. Additionally, the entire draft genome sequence was used to produce tiled microarrays in which noninterrupted sequence contigs were covered by consecutive 24-mer probes and associated mismatch probe sets. Total RNA isolated from cells grown in skim milk or in MRS to mid-log phase was used as a template to synthesize cDNA, followed by Cy3 labeling and hybridization. An analysis of data from annotated gene probes identified 42 genes that were upregulated during the growth of CNRZ32 in milk (P < 0.05), and 25 of these genes showed upregulation after applying Bonferroni's adjustment. The tiled microarrays identified numerous additional genes that were upregulated in milk versus MRS. Collectively, array data showed the growth of CNRZ32 in milk-induced genes encoding cell-envelope proteinases, oligopeptide transporters, and endopeptidases as well as enzymes for lactose and cysteine pathways, de novo synthesis, and/or salvage pathways for purines and pyrimidines and other functions. Genes for a hypothetical phosphoserine utilization pathway were also differentially expressed. Preliminary experiments indicate that cheese-derived, phosphoserine-containing peptides increase growth rates of CNRZ32 in a chemically defined medium. These results suggest that phosphoserine is used as an energy source during the growth of L. helveticus CNRZ32.     

Cells migrating to sites of tissue damage in response to the danger signal HMGB1 require NF-kappaB activation

Tissue damage is usually followed by healing, as both differentiated and stem cells migrate to replace dead or damaged cells. Mesoangioblasts (vessel-associated stem cells that can repair muscles) and fibroblasts migrate toward soluble factors released by damaged tissue. Two such factors are high mobility group box 1 (HMGB1), a nuclear protein that is released by cells undergoing unscheduled death (necrosis) but not by apoptotic cells, and stromal derived factor (SDF)-1/CXCL12. We find that HMGB1 activates the canonical nuclear factor kappaB (NF-kappaB) pathway via extracellular signal-regulated kinase phosphorylation. NF-kappaB signaling is necessary for chemotaxis toward HMGB1 and SDF-1/CXCL12, but not toward growth factor platelet-derived growth factor, formyl-met-leu-phe (a peptide that mimics bacterial invasion), or the archetypal NF-kappaB-activating signal tumor necrosis factor alpha. In dystrophic mice, mesoangioblasts injected into the general circulation ingress inefficiently into muscles if their NF-kappaB signaling pathway is disabled. These findings suggest that NF-kappaB signaling controls tissue regeneration in addition to early events in inflammation.