Sucrose interacts with auxin in the burst of axillary buds

Research focus. Branching is an important process for productivity (number of productive branches) and for visual quality of ornamental plants (branches spatial arrangement). But branching behaviour is difficult to predict due to the lack of knowledge on the all mechanisms regulating the plasticity of the burst of axillary buds. Auxin has an inhibitory action on bud burst and interacts with cytokinins (CKs) and strigolactones (SLs) [1]. Our study focuses on understanding and modelling how a newly - identified player, sugars [2,3], interact with the hormonal network to control bud burst . Methods. Experiments consisted in cultivating nodal stem segments of rosebush in vitro with different sucrose and auxin levels, and in quantifying bud elongation, CK level, and the expression of genes involve in SL biosynthesis and signalling. From these data, we designed and calibrated a computational model accounting for sucrose modulation of bud inhibition by auxin. Results. We observed that increasing sucrose level decreased the inhibition of bud elongation by auxin, so that buds fed with high sucrose level were less inhibited by a given amount of auxin than those fed with low sucrose level. In accordance with literature, auxin repressed CKs and stimulated the expression of SLs biosynthesis genes. We demonstrate that the main effect of sucrose was to repress SL signalling. The model developed from these results reproduced the combined action of sucrose and auxin on bud burst. We validated it for its capacity to predict the effect of external CK supply for different sucrose levels. Conclusions. Our study proposes for the first time a physiological model of the effect of sucrose on bud regulation by auxin at the scale of the bud. Initially observed for rosebush, our results were also validated in pea, demonstrating model genericity. Next step is to understand the role of sugars, together with hormones, in the spatio-temporal regulation of bud burst at the scale of the plant. For that, we will use the computational tool, by coupling our bud model to models simulating sugar and hormone fluxes within a plant architecture. (Texte intégral

The NE Atlantic region: a reappraisal of crustal structure, tectonostratigraphy and magmatic evolution: an introduction to the NAG-TEC project

The NE Atlantic region and its continental margins (Fig. 1) hold unique information for understanding many aspects of Earth science, from global geodynamics to palaeoceanography and global environmental change. It also holds some of the world's most important hydrocarbon reserves from the North Sea, along the Atlantic margins of Ireland, Britain and Norway, and into the Arctic in the Barents Sea. Historically, studies in the NE Atlantic were important for establishing many of the key ideas during the early part of the plate tectonic revolution. Linear magnetic anomalies along the Reykjanes Ridge were identified as early as in the 1960s (Heirtzler et al. 1966) and provided strong evidence for the seafloor spreading hypothesis (Dietz 1961), which by then had been established as a new and holistic theory (Ewing & Heezen 1956). At the same time, Iceland was already recognized as an intriguing anomalous entity (Böðvarsson & Walker 1964) and contributed to knowledge about how Earth's magnetic field reversed its polarity through time. The fact that rifting occurs in close association with old sutures and orogenic belts led Wilson to propose that the Atlantic Ocean closed and opened again, establishing the concept of the ‘Wilson tectonic cycle’ (Wilson 1966; Dewey 1969). The North Atlantic continental margins have long been considered as archetypal, and divergent margins world-wide are commonly described as ‘Atlantic-type passive margins’. However, it is now accepted that these so-called ‘passive’ margins remain dynamic long after break-up, including post-rift vertical movements of up to kilometre scale. The type examples for such epeirogenic movements being, once again, the North Atlantic margin

Sucrose interacts with auxin in the burst of axillary buds

National audienceResearch focus. Branching is an important process for productivity (number of productive branches) and for visual quality of ornamental plants (branches spatial arrangement). But branching behaviour is difficult to predict due to the lack of knowledge on the all mechanisms regulating the plasticity of the burst of axillary buds. Auxin has an inhibitory action on bud burst and interacts with cytokinins (CKs) and strigolactones (SLs) [1]. Our study focuses on understanding and modelling how a newly-identified player, sugars [2,3], interact with the hormonal network to control bud burst. Methods. Experiments consisted in cultivating nodal stem segments of rosebush in vitro with different sucrose and auxin levels, and in quantifying bud elongation, CK level, and the expression of genes involve in SL biosynthesis and signalling. From these data, we designed and calibrated a computational model accounting for sucrose modulation of bud inhibition by auxin. Results. We observed that increasing sucrose level decreased the inhibition of bud elongation by auxin, so that buds fed with high sucrose level were less inhibited by a given amount of auxin than those fed with low sucrose level. In accordance with literature, auxin repressed CKs and stimulated the expression of SLs biosynthesis genes. We demonstrate that the main effect of sucrose was to repress SL signalling. The model developed from these results reproduced the combined action of sucrose and auxin on bud burst. We validated it for its capacity to predict the effect of external CK supply for different sucrose levels. Conclusions. Our study proposes for the first time a physiological model of the effect of sucrose on bud regulation by auxin at the scale of the bud. Initially observed for rosebush, our results were also validated in pea, demonstrating model genericity. Next step is to understand the role of sugars, together with hormones, in the spatio-temporal regulation of bud burst at the scale of the plant. For that, we will use the computational tool, by coupling our bud model to models simulating sugar and hormone fluxes within a plant architecture

The importance of Portuguese Continental Shelf Waters to Balearic Shearwaters revealed by aerial census

The Balearic shearwater Puffinus mauretanicus is one of the most threatened seabirds in the world. To evaluate the abundance and distribution of Balearic Shearwaters in Portuguese Continental Shelf Waters, during the post-breeding period when migrating birds are outside the Mediterranean Sea, we conducted 5 aerial surveys between 2010 and 2014 (21 survey days covering 62,716 km2). Following a line transect method, observers recorded a total of 181 Balearic Shearwaters sightings. Using Distance sampling software, we estimated an overall species abundance (2010–2014) of 10,182, ranging between 2338 in 2010 and 23,221 individuals in 2012. During the 2012 post-breeding period, the Portuguese Continental Shelf Waters were used by up to 96.8% of the latest migratory population assessment. Considering Balearic Shearwater estimates per sampling block, there was a preference for the North and Center sectors of the Portuguese coast (respectively, 7058 and 1366 individuals) where several SPAs were already designated. We computed the annual and overall habitat predictive models for Balearic Shearwaters using a maximum entropy algorithm on MaxEnt software. In all models, the Balearic shearwater distribution was best predicted by mean chlorophyll concentration. Balearic Shearwaters are mostly present in shallow shelf and coastal waters particularly in the widest portions of the continental shelf. These areas are strongly influenced by upwelling, which concurs with the chlorophyll concentration being the most important predicting variable. Portuguese Continental Shelf Waters are one of the most important post-breeding grounds to the Balearic ShearwaterPortuguese Wildlife Society and projects SafeSea EEA-Grants, FAME (Proj. 2009-1/089) and European Commission’s Life Programme (MarPro NAT/PT/00038). This study was also partly supported by the Portuguese Foundation for Science and Technology (FCT) with Grants SFRH/ BD/30240/2006 to M. Ferreira and SFRH/BD/32841/2006 to P. C. Rodrigues. C. Eira is supported by FCT through CESAM UID/AMB/50017/2013 co-funded by FCT/MEC and FEDER, within PT2020 and Compete 2020 and S. Monteiro is financed by a Grant (BPD/0043/AMB/50017) from UID/AMB/50017/2013. This work was also partially supported by the strategic programme UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569) funded by FCT and by ERDF (COMPETE2020). The authors thank observers and airplane pilots who contributed to this workinfo:eu-repo/semantics/publishedVersio

Macro-invertébrés du Cénomanien du Djebel Metrassi (Batna, NE Algérie): Systématique et biostratigraphie

A rich paleontological assemblage was collected in the Cenomanian deposits of the Djebel Metrassi (Batna, NE Algeria). It consists of 327 specimens assigned respectively to a single coral, 24 bivalve, 14 gastropod, 3 ammonite, and 7 echinoid species. This macrofaunal association leads us to establish an original taxonomical reference list along with several species new for the Cenomanian of this area, and supports the lithostratigraphic framework herein proposed.[fr] Un assemblage paléontologique a été récolté dans le Cénomanien du Djebel Metrassi (Batna, NE Algérie). Constitué de 327 spécimens, il comporte un corail, 24 espèces de bivalves, 14 espèces de gastéropodes, 3 espèces d’ammonites et 7 espèces d’échinides. Cet assemblage permet d’établir une liste systématique originale, avec des espèces inédites, pour le Cénomanien de ce Djebel et vient soutenir le découpage lithostratigraphique proposé

Global assessment of marine plastic exposure risk for oceanic birds

Plastic pollution is distributed patchily around the world’s oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species

Environmental variability and population dynamics: do European and North American ducks play by the same rules?

Density dependence, population regulation, and variability in population size are fundamental population processes, the manifestation and interrelationships of which are affected by environmental variability. However, there are surprisingly few empirical studies that distinguish the effect of environmental variability from the effects of population processes. We took advantage of a unique system, in which populations of the same duck species or close ecological counterparts live in highly variable (north American prairies) and in stable (north European lakes) environments, to distinguish the relative contributions of environmental variability (measured as between-year fluctuations in wetland numbers) and intraspecific interactions (density dependence) in driving population dynamics. We tested whether populations living in stable environments (in northern Europe) were more strongly governed by density dependence than populations living in variable environments (in North America). We also addressed whether relative population dynamical responses to environmental variability versus density corresponded to differences in life history strategies between dabbling (relatively "fast species" and governed by environmental variability) and diving (relatively "slow species" and governed by density) ducks. As expected, the variance component of population fluctuations caused by changes in breeding environments was greater in North America than in Europe. Contrary to expectations, however, populations in more stable environments were not less variable nor clearly more strongly density dependent than populations in highly variable environments. Also, contrary to expectations, populations of diving ducks were neither more stable nor stronger density dependent than populations of dabbling ducks, and the effect of environmental variability on population dynamics was greater in diving than in dabbling ducks. In general, irrespective of continent and species life history, environmental variability contributed more to variation in species abundances than did density. Our findings underscore the need for more studies on populations of the same species in different environments to verify the generality of current explanations about population dynamics and its association with species life history.Peer reviewe