Plants Modify Biological Processes to Ensure Survival following Carbon Depletion: A Lolium perenne Model

BACKGROUND: Plants, due to their immobility, have evolved mechanisms allowing them to adapt to multiple environmental and management conditions. Short-term undesirable conditions (e.g. moisture deficit, cold temperatures) generally reduce photosynthetic carbon supply while increasing soluble carbohydrate accumulation. It is not known, however, what strategies plants may use in the long-term to adapt to situations resulting in net carbon depletion (i.e. reduced photosynthetic carbon supply and carbohydrate accumulation). In addition, many transcriptomic experiments have typically been undertaken under laboratory conditions; therefore, long-term acclimation strategies that plants use in natural environments are not well understood. METHODOLOGY/PRINCIPAL FINDINGS: Perennial ryegrass (Lolium perenne L.) was used as a model plant to define whether plants adapt to repetitive carbon depletion and to further elucidate their long-term acclimation mechanisms. Transcriptome changes in both lamina and stubble tissues of field-grown plants with depleted carbon reserves were characterised using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The RT-qPCR data for select key genes indicated that plants reduced fructan degradation, and increased photosynthesis and fructan synthesis capacities following carbon depletion. This acclimatory response was not sufficient to prevent a reduction (P<0.001) in net biomass accumulation, but ensured that the plant survived. CONCLUSIONS: Adaptations of plants with depleted carbon reserves resulted in reduced post-defoliation carbon mobilization and earlier replenishment of carbon reserves, thereby ensuring survival and continued growth. These findings will help pave the way to improve plant biomass production, for either grazing livestock or biofuel purposes

Ubiquitin Ligase RNF146 Regulates Tankyrase and Axin to Promote Wnt Signaling

Canonical Wnt signaling is controlled intracellularly by the level of β-catenin protein, which is dependent on Axin scaffolding of a complex that phosphorylates β-catenin to target it for ubiquitylation and proteasomal degradation. This function of Axin is counteracted through relocalization of Axin protein to the Wnt receptor complex to allow for ligand-activated Wnt signaling. AXIN1 and AXIN2 protein levels are regulated by tankyrase-mediated poly(ADP-ribosyl)ation (PARsylation), which destabilizes Axin and promotes signaling. Mechanistically, how tankyrase limits Axin protein accumulation, and how tankyrase levels and activity are regulated for this function, are currently under investigation. By RNAi screening, we identified the RNF146 RING-type ubiquitin E3 ligase as a positive regulator of Wnt signaling that operates with tankyrase to maintain low steady-state levels of Axin proteins. RNF146 also destabilizes tankyrases TNKS1 and TNKS2 proteins and, in a reciprocal relationship, tankyrase activity reduces RNF146 protein levels. We show that RNF146, tankyrase, and Axin form a protein complex, and that RNF146 mediates ubiquitylation of all three proteins to target them for proteasomal degradation. RNF146 is a cytoplasmic protein that also prevents tankyrase protein aggregation at a centrosomal location. Tankyrase auto-PARsylation and PARsylation of Axin is known to lead to proteasome-mediated degradation of these proteins, and we demonstrate that, through ubiquitylation, RNF146 mediates this process to regulate Wnt signaling

Liposomal Packaging Generates Wnt Protein with In Vivo Biological Activity

Wnt signals exercise strong cell-biological and regenerative effects of considerable therapeutic value. There are, however, no specific Wnt agonists and no method for in vivo delivery of purified Wnt proteins. Wnts contain lipid adducts that are required for activity and we exploited this lipophilicity by packaging purified Wnt3a protein into lipid vesicles. Rather than being encapsulated, Wnts are tethered to the liposomal surface, where they enhance and sustain Wnt signaling in vitro. Molecules that effectively antagonize soluble Wnt3a protein but are ineffective against the Wnt3a signal presented by a cell in a paracrine or autocrine manner are also unable to block liposomal Wnt3a activity, suggesting that liposomal packaging mimics the biological state of active Wnts. When delivered subcutaneously, Wnt3a liposomes induce hair follicle neogenesis, demonstrating their robust biological activity in a regenerative context

The chronostratigraphy of the Haua Fteah cave (Cyrenaica, northeast Libya)

The 1950s excavations by Charles McBurney in the Haua Fteah, a large karstic cave on the coast of northeast Libya, revealed a deep sequence of human occupation. Most subsequent research on North African prehistory refers to his discoveries and interpretations, but the chronology of its archaeological and geological sequences has been based on very early age determinations. This paper reports on the initial results of a comprehensive multi-method dating program undertaken as part of new work at the site, involving radiocarbon dating of charcoal, land snails and marine shell, cryptotephra investigations, optically stimulated luminescence (OSL) dating of sediments, and electron spin resonance (ESR) dating of tooth enamel. The dating samples were collected from the newly exposed and cleaned faces of the upper 7.5 m of the w14.0 m-deep McBurney trench, which contain six of the seven major cultural phases that he identified. Despite problems of sediment transport and reworking, using a Bayesian statistical model the new dating program establishes a robust framework for the five major lithostratigraphic units identified in the stratigraphic succession, and for the major cultural units. The age of two anatomically modern human mandibles found by McBurney in Layer XXXIII near the base of his Levalloiso-Mousterian phase can now be estimated to between 73 and 65 ka (thousands of years ago) at the 95.4% confidence level, within Marine Isotope Stage (MIS) 4. McBurney’s Layer XXV, associated with Upper Palaeolithic Dabban blade industries, has a clear stratigraphic relationship with Campanian Ignimbrite tephra. Microlithic Oranian technologies developed following the climax of the Last Glacial Maximum and the more microlithic Capsian in the Younger Dryas. Neolithic pottery and perhaps domestic livestock were used in the cave from the mid Holocene but there is no certain evidence for plant cultivation until the Graeco-Roman period

Tragicomic presentations of self : starring Phil Silvers as Bilko : the incomplete comic human

When a performer becomes over-associated with a particular, celebrated comic character can this lead to problems, not merely in terms of type-casting, but in creating confusions for the actor’s own perception of self? In instances where a comic creation is perceived to be an extension of the performer’s actual ‘self’, what dissonances in self construct may arise between the comic actor’s created persona and his/her own presentation of self? This article considers the nature of tensions created through the permeation of persona and person which can beset comedians who become closely identified with their particular mediated role. Can, indeed, over-association with their successful ‘signature’ comic role be seen to prove psychologically destabilising for certain performers whose own fragile, sense of identity becomes further compromised by presentation of their own most familiar and definitive, comic creations? Drawing specifically upon the career and comedy of Phil Silvers (aka ‘Sergeant ‘Bilko’), this article attempts to evaluate the forms of crises of identity that can arise between presentations of public and private selves for those performers who become, in effect, ‘public comic property’

Motor imagery during action observation: A brief review of evidence, theory and future research opportunities

Motor imagery (MI) and action observation (AO) have traditionally been viewed as two separate techniques, which can both be used alongside physical practice to enhance motor learning and rehabilitation. Their independent use has been shown to be effective, and there is clear evidence that the two processes can elicit similar activity in the motor system. Building on these well-established findings, research has now turned to investigate the effects of their combined use. In this article, we first review the available neurophysiological and behavioral evidence for the effects of combined action observation and motor imagery (‘AO+MI’) on motor processes. We next describe a conceptual framework for their combined use, and then discuss several areas for future research into AO+MI processes. In this review, we advocate a more integrated approach to AO+MI techniques than has previously been adopted by movement scientists and practitioners alike. We hope this early review of an emergent body of research, along with a related set of research questions, can inspire new work in this area. We are optimistic that future research will further confirm if, how, and when this combined approach to AO+MI can be more effective in motor learning and rehabilitation settings, relative to the more traditional application of AO or MI independently

Chronostratigraphy and ecology of two Middle and Upper Pleistocene sites (Jersey,Channel Islands)

Thanks to their coastal location on what is now an island on the continental shelf, the two early Middle Palaeolithic sites of La Cotte à la Chèvre and La Cotte de St Brelade are especially sensitive to environmental change. The former is a small sea-cave cut during a +18 m marine transgression. At the latter site no traces of this episode have been found, but the archaeologically very rich sediments of Saalian age were sculpted into a cliff during the +8 m transgression of isotope substage 5e, and were capped by a triple soil followed by thick Weichsehan deposits ; an earlier interglacial complex is dated to 238 ±35 ky, and must be attributed to oxygen isotope stage 7. Geology, flora and fauna combine to document a long sequence of environmental change. The deep ravine system is a natural sediment trap in which wind-transported materials - chiefly loess, and sand formed by decay of the granite bedrock - alternated in a manner clearly linked to climatic change. The occupation of the two sites appears to cover much the same chronological range. They may be regarded as complementary, in that if they were used by a single human group La Cotte à la Chèvre would have provided a convenient means of slightly extending the catchment of the much larger and better placed St Brelade site, which on archaeological evidence was a far more important focus of activity. Human presence in the area was controlled directly or indirectly by climate ; there appears to have been a 'window' within which the sea-level was low enough to permit easy access to Jersey while the cold was not severe as to inhibit activity altogether. The landscape would have varied from, at one extreme, a comparatively wooded peninsula attached to the Cotentin, to a tableland set in a broad coastal plain with more open vegetation. Perhaps the most remarkable aspect of Pleistocene Jersey is the clarity with which the close mutual interdependence between different components is revealed - climate, sedimentation and soil formation, sea-level changes and manne erosion, physical geography, fauna and flora, human presence and economy, supplies of raw material for tool-making and stone-working techniques.Les sites du paléolithique moyen ancien de La Cotte à la Chèvre et de La Cotte de St Brelade ont été particulièrement sensibles aux changements de l'environnement, du fait de leur position côtière sur ce qui est maintenant une île du plateau continental. Le premier site est une petite grotte marine, creusée lors d'une transgression de 18 m. Les traces de cet événement n'ont pas été retrouvées dans le deuxième site, mais des sédiments d'âge saalien, très riches d'un point de vue archéologique, ont été découpés en falaise durant la transgression de 8 m du sous-stade isotopique 5e des carottes océaniques et sont coiffés de trois sols suivis par des dépôts épais du Weichsélien. Un complexe interglaciaire plus ancien a été daté de 238 000±35 000 ans et appartient donc au stade isotopique 7. La géologie, la flore et la faune se combinent pour documenter une longue séquence de fluctuations dans l'environnement. Des matériaux éoliens ou locaux (principalement des lœss, et des sables provenant de l'altération des granites de la roche mère) furent déposés dans un système de ravins profonds, et y alternent d'une manière très clairement liée aux événements climatiques. L'occupation de ces deux sites semble avoir pris place durant la même période chronologique. Si l'on émet l'hypothèse de l'occupation par un seul groupe humain, La Cotte à la Chèvre aurait permis d'étendre légèrement un territoire économique centré sur le site plus grand et mieux placé de St Brelade qui, si l'on s'en remet à l'évidence archéologique, fut un foyer d'activité bien plus important. La présence humaine dans cette région fut contrôlée directement ou indirectement par le climat. Il semble y avoir eu des périodes durant lesquelles le niveau marin permettait l'accès facile de Jersey et où le froid n'était pas d'une sévérité suffisante pour inhiber toute activité. Le paysage semble avoir varié d'une péninsule relativement boisée, rattachée au Cotentin, à un plateau situé dans une plaine côtière à végétation plus ouverte. L'aspect le plus remarquable de Jersey durant le Pléistocène est l'évidence avec laquelle la dépendance mutuelle de composantes diverses est révélée : le climat, la sédimentation et la formation des sols, les changements du niveau marin et l'érosion marine, la géographie physique, la faune et la flore, la présence humaine et l'économie, les sources de matière première pour la fabrication d'outils et les techniques de travail de la pierre.Callow Paul. Chronostratigraphy and ecology of two Middle and Upper Pleistocene sites (Jersey,Channel Islands). In: Revue archéologique de Picardie, n°1-2, 1988. Cultures et industries lithiques en milieu lœssique. Actes du colloque international, Amiens 9-11 décembre 1986. pp. 17-24