Longitudinal growth of the Saccharina kelp embryo depends on actin filaments that control the formation of a corset-like structure composed of alginate.

The initiation of embryogenesis in the kelp Saccharina latissima is accompanied by significant anisotropy in cell shape. Using monoclonal antibodies, we show that this anisotropy coincides with a spatio-temporal pattern of accumulation of alginates in the cell wall of the zygote and embryo. Alginates rich in guluronates as well as sulphated fucans show a homogeneous distribution in the embryo throughout Phase I of embryogenesis, but mannuronate alginates accumulate mainly on the sides of the zygote and embryo, disappearing as the embryo enlarges at the start of Phase II.

MUM, a maternal unknown message, inhibits early establishment of the medio-lateral axis in the embryo of the kelp Saccharina latissima.

Brown algae are multicellular photosynthetic organisms that have evolved independently of plants and other algae. Here, we have studied the determinism of body axis formation in the kelp Saccharina latissima. After microdissection of the embryo, we show that the stalk, an empty cell that retains the embryo on the maternal tissue, represses longitudinal cell divisions in the early embryo, thereby reinforcing the establishment of the initial apico-basal axis.

Cell-Autonomous and Non-Cell-Autonomous Mechanisms Concomitantly Regulate the Early Developmental Pattern in the Kelp Embryo.

Brown algae are multicellular organisms that have evolved independently from plants and animals. Knowledge of the mechanisms involved in their embryogenesis is available only for the , , and , which are brown algae belonging to three different orders. Here, we address the control of cell growth and cell division orientation in the embryo of , a brown alga belonging to the order Laminariales, which grows as a stack of cells through transverse cell divisions until growth is initiated along the perpendicular axis.

From Maximum of Inter-Visit Times to Starving Random Walks.

Very recently, a fundamental observable has been introduced and analyzed to quantify the exploration of random walks: the time τ_{k} required for a random walk to find a site that it never visited previously, when the walk has already visited k distinct sites. Here, we tackle the natural issue of the statistics of M_{n}, the longest duration out of τ_{0},…,τ_{n-1}. This problem belongs to the active field of extreme value statistics, with the difficulty that the random variables τ_{k} are both correlated and nonidentically distributed.

Repeated co-option of HMG-box genes for sex determination in brown algae and animals.

In many eukaryotes, genetic sex determination is not governed by XX/XY or ZW/ZZ systems but by a specialized region on the poorly studied U (female) or V (male) sex chromosomes. Previous studies have hinted at the existence of a dominant male-sex factor on the V chromosome in brown algae, a group of multicellular eukaryotes distantly related to animals and plants. The nature of this factor has remained elusive.

Interactions between U and V sex chromosomes during the life cycle of Ectocarpus.

In many animals and flowering plants, sex determination occurs in the diploid phase of the life cycle with XX/XY or ZW/ZZ sex chromosomes. However, in early diverging plants and most macroalgae, sex is determined by female (U) or male (V) sex chromosomes in a haploid phase called the gametophyte. Once the U and V chromosomes unite at fertilization to produce a diploid sporophyte, sex determination no longer occurs, raising key questions about the fate of the U and V sex chromosomes in the sporophyte phase.

Toward a coordinated understanding of hydro-biogeochemical root functions in tropical forests for application in vegetation models.

Tropical forest root characteristics and resource acquisition strategies are underrepresented in vegetation and global models, hampering the prediction of forest-climate feedbacks for these carbon-rich ecosystems. Lowland tropical forests often have globally unique combinations of high taxonomic and functional biodiversity, rainfall seasonality, and strongly weathered infertile soils, giving rise to distinct patterns in root traits and functions compared with higher latitude ecosystems. We provide a roadmap for integrating recent advances in our understanding of tropical forest belowground function into vegetation models, focusing on water and nutrient acquisition.

Whole-brain gray matter maturation trajectories associated with autistic traits from adolescence to early adulthood.

A growing number of evidence supports a continued distribution of autistic traits in the general population. However, brain maturation trajectories of autistic traits as well as the influence of sex on these trajectories remain largely unknown. We investigated the association of autistic traits in the general population, with longitudinal gray matter (GM) maturation trajectories during the critical period of adolescence.

Real-time quality control of optical backscattering data from Biogeochemical-Argo floats.

Background: Biogeochemical-Argo floats are collecting an unprecedented number of profiles of optical backscattering measurements in the global ocean. Backscattering (BBP) data are crucial to understanding ocean particle dynamics and the biological carbon pump. Yet, so far, no procedures have been agreed upon to quality control BBP data in real time.

Universal exploration dynamics of random walks.

The territory explored by a random walk is a key property that may be quantified by the number of distinct sites that the random walk visits up to a given time. We introduce a more fundamental quantity, the time τ required by a random walk to find a site that it never visited previously when the walk has already visited n distinct sites, which encompasses the full dynamics about the visitation statistics. To study it, we develop a theoretical approach that relies on a mapping with a trapping problem, in which the spatial distribution of traps is continuously updated by the random walk itself.

Parallel evolution of amphioxus and vertebrate small-scale gene duplications.

Background: Amphioxus are non-vertebrate chordates characterized by a slow morphological and molecular evolution. They share the basic chordate body-plan and genome organization with vertebrates but lack their 2R whole-genome duplications and their developmental complexity. For these reasons, amphioxus are frequently used as an outgroup to study vertebrate genome evolution and Evo-Devo.

From individual-based epidemic models to McKendrick-von Foerster PDEs: a guide to modeling and inferring COVID-19 dynamics.

We present a unifying, tractable approach for studying the spread of viruses causing complex diseases requiring to be modeled using a large number of types (e.g., infective stage, clinical state, risk factor class).

Complete visitation statistics of one-dimensional random walks.

We develop a framework to determine the complete statistical behavior of a fundamental quantity in the theory of random walks, namely, the probability that n_{1},n_{2},n_{3},...

Targeted Laser Ablation in the Embryo of Saccharina latissima.

In Saccharina latissima, the embryo develops as a monolayered cell sheet called the lamina or the blade. Each embryo cell is easy to observe, readily distinguishable from its neighbors, and can be individually targeted. For decades, laser ablation has been used to study embryo development.

Boundary conductance in macroscopic bismuth crystals.

The interface between a solid and vacuum can become electronically distinct from the bulk. This feature, encountered in the case of quantum Hall effect, has a manifestation in insulators with topologically protected metallic surface states. Non-trivial Berry curvature of the Bloch waves or periodically driven perturbation are known to generate it.

Bioluminescence and Photoreception in Unicellular Organisms: Light-Signalling in a Bio-Communication Perspective.

Bioluminescence, the emission of light catalysed by luciferases, has evolved in many taxa from bacteria to vertebrates and is predominant in the marine environment. It is now well established that in animals possessing a nervous system capable of integrating light stimuli, bioluminescence triggers various behavioural responses and plays a role in intra- or interspecific visual communication. The function of light emission in unicellular organisms is less clear and it is currently thought that it has evolved in an ecological framework, to be perceived by visual animals.

Universal kinetics of imperfect reactions in confinement.

Chemical reactions generically require that particles come into contact. In practice, reaction is often imperfect and can necessitate multiple random encounters between reactants. In confined geometries, despite notable recent advances, there is to date no general analytical treatment of such imperfect transport-limited reaction kinetics.

Emergent Shared Intentions Support Coordination During Collective Musical Improvisations.

Human interactions are often improvised rather than scripted, which suggests that efficient coordination can emerge even when collective plans are largely underspecified. One possibility is that such forms of coordination primarily rely on mutual influences between interactive partners, and on perception-action couplings such as entrainment or mimicry. Yet some forms of improvised joint actions appear difficult to explain solely by appealing to these emergent mechanisms.

Cell response to substrate rigidity is regulated by active and passive cytoskeletal stress.

Morphogenesis, tumor formation, and wound healing are regulated by tissue rigidity. Focal adhesion behavior is locally regulated by stiffness; however, how cells globally adapt, detect, and respond to rigidity remains unknown. Here, we studied the interplay between the rheological properties of the cytoskeleton and matrix rigidity.

Looking at New Unexpected Disease Targets in -Linked Lipodystrophies in the Light of Complex Cardiovascular Phenotypes: Implications for Clinical Practice.

Variants in , encoding A-type lamins, are responsible for laminopathies including muscular dystrophies, lipodystrophies, and progeroid syndromes. Cardiovascular laminopathic involvement is classically described as cardiomyopathy in striated muscle laminopathies, and arterial wall dysfunction and/or valvulopathy in lipodystrophic and/or progeroid laminopathies. We report unexpected cardiovascular phenotypes in patients with -associated lipodystrophies, illustrating the complex multitissular pathophysiology of the disease and the need for specific cardiovascular investigations in affected patients.

To remain or leave: Dispersal variation and its genetic consequences in benthic freshwater invertebrates.

Unlabelled: Variation in dispersal capacity may influence population genetic variation and relatedness of freshwater animals thus demonstrating how life-history traits influence patterns and processes that in turn influence biodiversity. The majority of studies have focused on the consequences of dispersal variation in taxa inhabiting riverine systems whose dendritic nature and upstream/downstream gradients facilitate characterizing populations along networks. We undertook extensive, large-scale investigations of the impacts of hydrological connectivity on population genetic variation in two freshwater bryozoan species whose dispersive propagules (statoblasts) are either attached to surfaces () or are released as buoyant stages () and that live primarily in either lotic () or lentic environments ().

Evolutionary Toxicogenomics of the Striped Killifish () in the New Bedford Harbor (Massachusetts, USA).

In this paper, we used a Genotyping-by-Sequencing (GBS) approach to find and genotype more than 4000 genome-wide SNPs (Single Nucleotide Polymorphisms) from striped killifish exposed to a variety of polychlorinated biphenyls (PCBs) and other aromatic pollutants in New Bedford Harbor (NBH, Massachusetts, USA). The aims of this study were to identify the genetic consequences of exposure to aquatic pollutants and detect genes that may be under selection. Low genetic diversity ( and π) was found in the site exposed to the highest pollution level, but the pattern of genetic diversity did not match the pollution levels.