The interplay between increased tooth crown‐height and chewing efficiency,and implications for Cervidae evolution

Mammals of numerous lineages have evolved high‐crowned (hypsodont) teeth particularly during the last 20 million years. This major phenotypic change is one of the most widely studied evolutionary phenomena in a broad range of disciplines, though the mechanisms underlying its transformation remain unresolved. Here, we present the first Finite Element Analysis (FEA) to investigate the alternative hypothesis that there is a biomechanical link between increased hypsodonty and a more effective mastication in deer. Our FE experiments compared patterns of stress and strain within and between different fossil and living species under different loading conditions, and found that more hypsodont teeth are suited for restricting stresses to those areas where chewing loading occurs. This mechanical improvement is consequence of specific and pronounced variations in tooth geometry and morphology of the occlusal surface that are strongly related to crown growth in the vertical plane. We demonstrate that hypsodonty enables selenodont‐teeth to adopt a mechanically improved design that increases the pressure whilst shearing foods. As ruminants are physiologically limited by both the quantity of food consumed and the time spent in the mastication and digestion, hypsodonty is highly advantageous when feeding on mechanically resistant, tough and fibrous foods. Consequently, it allows grass‐eaters to spend less time chewing, thereby increasing the volume of food ingested and/or providing more time for digestion. This study provides a promising line of evidences in support of biomechanical effectiveness, in addition to or instead of increased wear resistance, as a factor in explaining the evolutionary origins of the hypsodont phenotype.     

Tuning of the FMN binding and oxido-reduction properties by neighboring side chains in Anabaena flavodoxin

Contribution of three regions (phosphate-binding, 50’s and 90’s loops) of Anabaena apoflavodoxin to FMN binding and reduction potential was studied. Thr12 and Glu16 did not influence FMN redox properties, but Thr12 played a role in FMN binding. Replacement of Trp57 with Glu, Lys or Arg moderately shifted E_ox/sq and E_sq/hq and altered the energetic of the FMN redox states binding profile. Our data indicate that the side chain of position 57 does not modulate E_ox/sq by aromatic stacking or solvent exclusion, but rather by influencing the relative strength of the H-bond between the N(5) of the flavin and the Asn58-Ile59 bond. A correlation was observed between the isoalloxazine increase in solvent accessibility and less negative E_sq/hq. Moreover, E_sq/hq became less negative as positively charged residues were added near to the isoalloxazine. Ile59 and Ile92 were simultaneously mutated to Ala or Glu. These mutations impaired FMN binding, while shifting E_sq/hq to less negative values and E_ox/sq to more negative. These effects are discussed on the bases of the X-ray structures of some of the Fld mutants, suggesting that in Anabaena Fld the structural control of both electron transfer steps is much more subtle than in other Flds.     

Advanced microbial analysis for wastewater quality monitoring: metagenomics trend

Applied Microbiology and Biotechnology - Urban Wastewater treatment plants (UWWTPs) have played an important and fundamental role in society for water purification of contaminated human wastewaters...     

Discovery and characterization of two new stem rust resistance genes in <Emphasis Type="Italic">Aegilops sharonensis</Emphasis>

Key message

We identified two novel wheat stem rust resistance genes, Sr-1644-1Sh and Sr-1644-5Sh in Aegilops sharonensis that are effective against widely virulent African races of the wheat stem rust pathogen.

Abstract

Stem rust is one of the most important diseases of wheat in the world. When single stem rust resistance (Sr) genes are deployed in wheat, they are often rapidly overcome by the pathogen. To this end, we initiated a search for novel sources of resistance in diverse wheat relatives and identified the wild goatgrass species Aegilops sharonesis (Sharon goatgrass) as a rich reservoir of resistance to wheat stem rust. The objectives of this study were to discover and map novel Sr genes in Ae. sharonensis and to explore the possibility of identifying new Sr genes by genome-wide association study (GWAS). We developed two biparental populations between resistant and susceptible accessions of Ae. sharonensis and performed QTL and linkage analysis. In an F₆ recombinant inbred line and an F₂ population, two genes were identified that mapped to the short arm of chromosome 1S^sh, designated as Sr-1644-1Sh, and the long arm of chromosome 5S^sh, designated as Sr-1644-5Sh. The gene Sr-1644-1Sh confers a high level of resistance to race TTKSK (a member of the Ug99 race group), while the gene Sr-1644-5Sh conditions strong resistance to TRTTF, another widely virulent race found in Yemen. Additionally, GWAS was conducted on 125 diverse Ae. sharonensis accessions for stem rust resistance. The gene Sr-1644-1Sh was detected by GWAS, while Sr-1644-5Sh was not detected, indicating that the effectiveness of GWAS might be affected by marker density, population structure, low allele frequency and other factors.

     

Interactions between phenolic compounds present in dry olive residues and the arbuscular mycorrhizal symbiosis

The use of “alpeorujo” (dry olive residue) has been proposed as an organic amendment in order to enhance soil structure and to increase C storage in soils. The aim of this work is to study how aqueous alpeorujo (ADOR) extracts bioremediated with white-rot fungi and three representative phenolic acids present in this extract (protocatechuic, vanillic and caffeic acid) affect the growth of the arbuscular mychorrhizal fungus Rhizophagus custos in monoxenic culture. Our results show that ADOR decreased mycorrhization parameters; however, this negative effect ceased after ADOR bioremediation. Although protocatechuic and vanillic acids have drastic negative effects at high concentrations, these phenols enhance mycorrhization processes at low concentrations and caffeic acid negatively affects symbiosis at low concentrations. Finally, the capacity of root biomass to dissipate individual phenols was also estimated, in which mycorrhized roots improve phenol dissipation in the growth medium in the presence of different phenols. This study highlights the important role played by arbuscular mycorrhiza in protecting plants from phytotoxicity.     

Occurrence and Relatedness of Vancomycin-Resistant Enterococci in Animals, Humans, and the Environment in Different European Regions

Vancomycin-resistant enterococcci (VRE) in Europe are thought to have emerged partly due to the use of the glycopeptide avoparcin in animal husbandry. We compared the occurrence of VRE in geographical regions of Europe in which until 1997 large amounts of avoparcin were used (Spain, United Kingdom, and Denmark) with the occurrence of VRE in Sweden, where avoparcin was banned in 1986. We also studied the relatedness between VRE strains from different regions and habitats. In total, 2,580 samples were collected from humans, animals, and the environment (soil, sewage, recipient water). VRE resistant to 20 μg/ml vancomycin were identified in 8.2% of the samples and were found most frequently in raw and treated urban sewage samples (means, 71% and 36% of the samples, respectively), pig manure (17%), and hospital sewage (16%). The proportions of VRE-positive sewage samples were similar in Sweden, Spain, and the United Kingdom, whereas pig feces and manure were more often positive in Spain than in Sweden (30% versus 1%). Most VRE were Enterococcus faecium carrying vanA, and computerized biochemical phenotyping of the isolates of different ecological origins showed a high degree of polyclonality. In conclusion, it seems that animal-associated VRE probably reflect the former use of avoparcin in animal production, whereas VRE in human-associated samples may be a result of antibiotic use in hospitals. Since there seems to be a reservoir of the resistance genes in all countries studied, precautions must be taken to limit the use of antibiotics and antibiotic-like feed additives.     

Influence of recovery method and microbial contamination on the response to freezing–thawing in ibex (Capra pyrenaica) epididymal spermatozoa

The method of sperm recovery may influence the initial quality of sperm samples and their response to freezing–thawing. The aim of the present work was to compare two methods for collecting epididymal spermatozoa in order to improve the quality of recovered sperm and reduce possible contamination. Testes were obtained from 23 legally hunted, adult ibex males. The sperm mass of the right epididymis was collected by small longitudinal and transverse cuts made in the cauda epididymidis. The sperm mass of the left epididymis was collected by retrograde flushing from the vas deferens to the cauda epididymidis (using a cannula), employing a Tris, citric acid, glucose, egg yolk-based medium. The flushing method recovered more spermatozoa (P < 0.001) than the cutting method. After freezing–thawing, greater acrosomes damage (P < 0.001) and more morphological abnormalities (P < 0.05) were seen among the sperm cells recovered by the cutting method than among those obtained by retrograde flushing. The method of sperm recovery did not, however, influence the microbial contamination rate. In frozen–thawed samples that were microbially contaminated, motility was significantly reduced (P < 0.05) and membrane integrity tended to be poorer (P = 0.06). In conclusion, retrograde flushing is recommended for ibex sperm collection since it would appear that microbial contamination is no more of a problem than that encountered with the cutting method, while a larger number of sperm cells more resistant to freezing–thawing can be obtained.     

Cell wall polysaccharides isolated from the fungus <Emphasis Type="Italic">Neotestudina rosatii</Emphasis>, one of the etiologic agents of mycetoma in man

The alkali-extractable water-soluble polysaccharides F1SS isolated from the cell wall of two isolates of the pathogen Neotestudina rosatii and one of Pseudophaeotrichum sudanense, which is now considered as a synonym of the former, have been studied by methylation analysis, GC–MS and NMR spectroscopy. The three polysaccharides differ mainly in their content in galactofuranose, and have the following idealized repeating unit:      

Plk3 Interacts with and Specifically Phosphorylates VRK1 in Ser342, a Downstream Target in a Pathway That Induces Golgi Fragmentation

Golgi fragmentation is a process that is necessary to allow its redistribution into daughter cells during mitosis, a process controlled by serine-threonine kinases. This Golgi fragmentation is activated by MEK1 and Plk3. Plk3 is a kinase that is a downstream target in the Golgi fragmentation pathway induced by MEK1 or by nocodazole. In this work, we have identified that Plk3 and VRK1 are two consecutive steps in this signaling pathway. Plk3 interacts with VRK1, forming a stable complex detected by reciprocal immunoprecipitations and pull-down assays; VRK1 colocalizes with giantin in the Golgi apparatus, as Plk3 also does, forming clearly detectable granules. VRK1 does not phosphorylate Plk3, but Plk3 phosphorylates the C-terminal region of VRK1 in Ser342. VRK1 with substitutions in S342 is catalytically active but blocks Golgi fragmentation, indicating that its specific phosphorylation is necessary for this process. The induction of Golgi fragmentation by MEK1 and Plk3 can be inhibited by kinase-dead VRK1, the knockdown of VRK1 by siVRK1, kinase-dead Plk3, or PD98059, a MEK1 inhibitor. The Plk3-VRK1 kinase module might represent two consecutive steps of a signaling cascade that participates in the regulation of Golgi fragmentation.The Golgi apparatus in mammalian cells is formed by cistern stacks, tubules, and small vesicles, which undergo extensive and sequential fragmentation in mitosis (33). The reorganization of the Golgi apparatus, involving fragmentation, dispersal, and reassembly, is tightly regulated during mitosis (1, 27, 30), and reversible phosphorylation plays a critical role (1, 21), although the components and their sequential organization in the context of the initiation or execution of the signal required for Golgi fragmentation are only partially known.Many signaling pathways are composed of consecutive kinases. Characterization of new signaling pathways requires the identification of their components, the connections between them, and the order in which they are organized. Human VRK1 is a novel serine-threonine kinase that phosphorylates several proteins implicated in cellular responses to stress and DNA damage, such as p53 (5, 20, 40), c-Jun (31), and ATF2 (32), as well as proteins needed for nuclear envelope assembly required at the end of mitosis, such as Baf (25). In addition, VRK1 kinase activity is inhibited by interaction with RanGDP, and this inhibition is relieved by RanGTP, suggesting an asymmetric distribution of its activity within the nucleus and in mitosis (29). These properties suggest that the VRK1 gene plays a role in the regulation of cell cycle initiation and/or progression, consistent with its requirement for entry into the cell cycle, where it behaves as an immediate-early response gene like c-MYC and FOS (36). The loss of VRK1 by use of small interfering RNA (siRNA) induces an early G₁ block, before cyclin D1 expression (36), which is accompanied by a reduction in the phospho-retinoblastoma level and an accumulation of cycle inhibitors, such as p27 (36), resulting in a stop in cell cycle progression (36, 40).Several kinases are implicated in the control of cell proliferation and in different mitotic checkpoints; among them are the polo-like kinase (Plk) family, which is a group composed of four proteins (14, 39, 46). One of them, Plk3, contributes as a mediator of DNA damage checkpoint responses, since its kinase activity increases after oxidative stress (43) and induction of DNA damage by ionizing radiomimetic drugs (45). Plk3 physically interacts with and phosphorylates p53 in Ser20, and this interaction increases in response to DNA damage and induces either cell cycle arrest or apoptosis (44) so that genetic stability can be maintained by the prevention of the accumulation of genetic damage. Furthermore, Plk3 interacts with Chk2 (2, 45), an important mediator of DNA damage responses (6, 16), and there is a functional connection between them since Plk3 phosphorylates Chk2 in Ser62 and Ser73, which are necessary for full Chk2 activation by ATM (4). In mitotic cells, Plk3 is localized associated with the spindle poles and mitotic spindles, and deregulated expression of Plk3 induces cell cycle arrest and apoptosis by the perturbation of microtubule integrity (41). In addition, Plk3 expression is induced after mitogenic stimulation, and it is required for mitotic (28) and S-phase (48) entry. Plk3 also regulates Cdc25C (3, 23, 26) and the NF-κB signaling pathway (19). VRK1 phosphorylates p53 in Thr18 (20, 40), a residue phosphorylated in response to taxol, an inhibitor of microtubule polymerization (34).There is a possibility that VRK1 and Plk3 might be connected in some way, since subpopulations of both VRK1 (37) and Plk3 (28) have been detected in the Golgi apparatus near the centrosome, where they colocalize with Golgi markers such as giantin or GM130 (33). Golgi fragmentation can be induced by MEK1 (1, 15), and this signal is partly mediated by Plk3 (28, 42). Moreover, Golgi fragmentation is a required step during mitosis, occurring late in the G₂/M phase of the cell cycle (11), and MEK1 is implicated in the activation of this process (1, 15).The common biological aspects of VRK1 and Plk3 proteins and the association of VRK1 and Plk3 subpopulations in the Golgi apparatus led us to think that there might be a functional connection between these two kinases and thus that they might be components in a common signaling pathway. In this work, we explored the possible connection between VRK1 and Plk3 and determined if they were functionally related in a biological process, Golgi fragmentation, in which one of them, Plk3, is already known to participate. This work demonstrates that Plk3 and VRK1 are consecutive components in the signaling pathway that induces Golgi fragmentation in mitosis.