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Choanoflagellates offer key insights into bacterial influences on the origin and early evolution of animals. Here we report the isolation and characterization of a new colonial choanoflagellate species, Barroeca monosierra, that, unlike previously characterized species, harbors a microbiome. B. monosierra was isolated from Mono Lake, California and forms large spherical colonies that are more than an order of magnitude larger than those formed by the closely related Salpingoeca rosetta. By designing fluorescence in situ hybridization probes from metagenomic sequences, we found that B. monosierra colonies are colonized by members of the halotolerant and closely related Saccharospirillaceae and Oceanospirillaceae, as well as purple sulfur bacteria (Ectothiorhodospiraceae) and non-sulfur Rhodobacteraceae. This relatively simple microbiome in a close relative of animals presents a new experimental model for investigating the evolution of stable interactions among eukaryotes and bacteria.IMPORTANCEThe animals and bacteria of Mono Lake (California) have evolved diverse strategies for surviving the hypersaline, alkaline, arsenic-rich environment. We sought to investigate whether the closest living relatives of animals, the choanoflagellates, exist among the relatively limited diversity of organisms in Mono Lake. We repeatedly isolated members of a single species of choanoflagellate, which we have named Barroeca monosierra, suggesting that it is a stable and abundant part of the ecosystem. Characterization of B. monosierra revealed that it forms large spherical colonies that each contain a microbiome, providing an opportunity to investigate the evolution of stable physical associations between eukaryotes and bacteria.

De acuerdo con la rigurosa labor que el Instituto Andaluz del Patrimonio Histórico (IAPH) lleva promoviendo desde los años 90 del siglo XX en materia de divulgación del patrimonio cultural y, más concretamente, en consonancia con el trabajo de documentación, investigación y gestión del patrimonio cultural inmaterial (PCI) que desde el Centro de Documentación y Estudios de dicha institución llevan desarrollando, prácticamente, desde su constitución, su más reciente publicación, esto es, La salvaguarda del patrimonio inmaterial como acuerdo social. Propuesta metodológica para la elaboración de planes colaborativos de salvaguarda del PCI, se presenta como el desenlace lógico de dicho ingente trabajo para la salvaguarda del PCI que tuvo como punto de partida la elaboración del Atlas del Patrimonio Inmaterial de Andalucía (2008-2014). Este monográfico, por su parte, profundiza en esa misma senda en tanto que supone un determinante salto epistemológico en la superación del discurso autorizado del patrimonio y un contundente alegato en pro de la apertura de “ventas de flexibilidad” en lo respectivo a la gestión (participativa) del PCI, entendida ésta como un acuerdo social entre los agentes implicados

Summary Small RhoGTPases direct cell shape changes and movements during tissue morphogenesis. Their activities are tightly regulated in space and time to specify the desired pattern of actomyosin contractility that supports tissue morphogenesis. This is expected to stem from polarized surface stimuli and from polarized signaling processing inside cells. We examined this general problem in the context of cell intercalation that drives extension of the Drosophila ectoderm. In the ectoderm, G protein-coupled receptors (GPCRs) and their downstream heterotrimeric G proteins (Gα and Gβγ) activate Rho1 both medial-apically, where it exhibits pulsed dynamics, and at junctions, where its activity is planar polarized. However, the mechanisms responsible for polarizing Rho1 activity are unclear. We report that distinct guanine exchange factors (GEFs) activate Rho1 in these two cellular compartments. RhoGEF2 acts uniquely to activate medial-apical Rho1 but is recruited both medial-apically and at junctions by Gα12/13-GTP, also called Concertina (Cta) in Drosophila. On the other hand, Dp114RhoGEF (Dp114), a newly characterized RhoGEF, is required for cell intercalation in the extending ectoderm, where it activates Rho1 specifically at junctions. Its localization is restricted to adherens junctions and is under Gβ13F/Gγ1 control. Furthermore, Gβ13F/Gγ1 activates junctional Rho1 and exerts quantitative control over planar polarization of Rho1. Finally, we found that Dp114RhoGEF is absent in the mesoderm, arguing for a tissue-specific control over junctional Rho1 activity. These results clarify the mechanisms of polarization of Rho1 activity in different cellular compartments and reveal that distinct GEFs are sensitive tuning parameters of cell contractility in remodeling epithelia., Graphical Abstract, Highlights • Dp114RhoGEF activates junctional Rho1 and is involved in cell intercalation • Gα/Cta and Gβγ subunits tune, respectively, RhoGEF2 and Dp114RhoGEF membrane levels • Gβγ subunits control planar polarity of junctional Rho1 signaling via Dp114RhoGEF • Tissue-specific RhoGEFs could diversify morphogenesis in different tissues, Garcia De Las Bayonas et al. investigate the spatial control of Rho1 signaling that drives contractility during epithelial morphogenesis. They identify two RhoGEFs, which independently activate Rho1 at the medio-apical and junctional compartments in intercalating cells. This process requires upstream control by distinct heterotrimeric G proteins.

Small RhoGTPases and Myosin-II direct cell shape changes and movements during tissue morphogenesis. Their activities are tightly regulated in space and time to specify the desired pattern of contractility that supports tissue morphogenesis. This is expected to stem from polarized surface stimuli and from polarized signaling processing inside cells. We examined this general problem in the context of cell intercalation that drives extension of theDrosophilaectoderm. In the ectoderm, G protein coupled receptors (GPCRs) and their downstream heterotrimeric G proteins (Gα and Gβγ) activate Rho1 both medial-apically, where it exhibits pulsed dynamics, and at junctions, where its activity is planar polarized (Kerridge et al., 2016; Munjal et al., 2015). However, the mechanisms responsible for polarizing Rho1 activity are unclear. In particular, it is unknown how Rho1 activity is controlled at junctions. We report a division of labor in the mechanisms of Rho1 activation in that distinct guanine exchange factors (GEFs), that serve as activators of Rho1, operate in these distinct cellular compartments. RhoGEF2 acts uniquely to activate medial-apical Rho1. Although RhoGEF2 is recruited both medial-apically and at junctions by Gα12/13-GTP, also called Concertina (Cta) inDrosophila, its activity is restricted to the medial-apical compartment. Furthermore, we characterize a novel RhoGEF, p114RhoGEF/Wireless (Wrl), and report its requirement for cell intercalation in the extending ectoderm. p114RhoGEF/Wireless activates Rho1 specifically at junctions. Strikingly it is restricted to adherens junctions and is under Gβ13F/Gγ1 control. Gβ13F/Gγ1 activates junctional Rho1 and exerts quantitative control over planar polarization of Rho1. In particular, overexpression of Gβ13F/Gγ1 leads to hyper planar polarization of Rho1 and MyoII. Finally, we found that p114RhoGEF/Wireless is absent in the mesoderm, arguing for a tissue-specific control over junctional Rho1 activity. These results shed light on the mechanisms of polarization of Rho1 activity in different cellular compartments and reveal that distinct GEFs are sensitive tuning parameters of cell contractility in remodeling epithelia.

In this issue of Developmental Cell, Acharya et al. (2018) uncover a mechanosensitive pathway that activates RhoA in epithelial cells exposed to acute tensile stress. This pathway serves to preserve tissue integrity via regulation of tensile strength, the threshold force above which adherens junctions rupture.

International audience; Polarized cell shape changes during tissue morphogenesis arise by controlling the subcellular distribution of myosin II. For instance, during Drosophila melanogaster gastrulation, apical constriction and cell intercalation are mediated by medial-apical myosin II pulses that power deformations, and polarized accumulation of myosin II that stabilizes these deformations. It remains unclear how tissue-specific factors control different patterns of myosin II activation and the ratchet-like myosin II dynamics. Here we report the function of a common pathway comprising the heterotrimeric G proteins Gα12/13, Gβ13F and Gγ1 in activating and polarizing myosin II during Drosophila gastrulation. Gα12/13 and the Gβ13F/γ1 complex constitute distinct signalling modules, which regulate myosin II dynamics medial-apically and/or junctionally in a tissue-dependent manner. We identify a ubiquitously expressed GPCR called Smog required for cell intercalation and apical constriction. Smog functions with other GPCRs to quantitatively control G proteins, resulting in stepwise activation of myosin II and irreversible cell shape changes. We propose that GPCR and G proteins constitute a general pathway for controlling actomyosin contractility in epithelia and that the activity of this pathway is polarized by tissue-specific regulators.

A new procedure for constructing an optical fibre reflectance, bulk optode membrane type, sensor is presented. The optode membrane consists of a plasticized poly (vinyl chloride) membrane in which the ionophore is dissolved, entrapped in a cellulose support. The new optode with the dye indicator 1-(2-pyridylazo)-2-naphthol (PAN) was incorporated in a new flow-through cell and the injection system was optimized to determine Cu (II) at 567 nm in the range 5 x 10(-5)-10(-3) M. The response was reproducible and the optode can be regenerated using 10(-2) M EDTA followed by water. The method was applied to the determination of copper in real samples.