Varied effects of algal symbionts on transcription factor NF-κB in a sea anemone and a coral: possible roles in symbiosis and thermotolerance

Many cnidarians, including the reef-building corals, undergo symbiotic mutualisms with photosynthetic dinoflagellate algae of the family Symbiodiniaceae. These partnerships are sensitive to temperature extremes, which cause symbiont loss and increased coral mortality. Previous studies have implicated host immunity and specifically immunity transcription factor NF-κB as having a role in the maintenance of the cnidarian-algal symbiosis. Here we have further investigated a possible role for NF-κB in establishment and loss of symbiosis in various strains of the anemone Exaiptasia (Aiptasia) and in the coral Pocillopora damicornis. Our results show that NF-κB expression is reduced in Aiptasia larvae and adults that host certain algae strains. Treatment of Aiptasia larvae with a known symbiosis-promoting cytokine, transforming growth factor β, also led to decreased NF-κB expression. We also show that aposymbiotic Aiptasia (with high NF-κB expression) have increased survival following infection with the pathogenic bacterium Serratia marcescens as compared to symbiotic Aiptasia (low NF-κB expression). Furthermore, a P. damicornis coral colony hosting Durusdinium spp. (formerly clade D) symbionts had higher basal NF-κB expression and decreased heat-induced bleaching as compared to two individuals hosting Cladocopium spp. (formerly clade C) symbionts. Lastly, genome-wide gene expression profiling and genomic promoter analysis identified putative NF-κB target genes that may be involved in thermal bleaching, symbiont maintenance, and/or immune protection in P. damicornis. Our results provide further support for the hypothesis that modulation of NF-κB and immunity plays a role in some, but perhaps not all, cnidarian-Symbiodiniaceae partnerships as well as in resistance to pathogens and bleaching.Accepted manuscrip

Self-patterning of human stem cells into post-implantation lineages

Investigating human development is a substantial scientific challenge due to the technical and ethical limitations of working with embryonic samples. In the face of these difficulties, stem cells have provided an alternative to experimentally model inaccessible stages of human development in vitro1,2,3,4,5,6,7,8,9,10,11,12,13. Here we show that human pluripotent stem cells can be triggered to self-organize into three-dimensional structures that recapitulate some key spatiotemporal events of early human post-implantation embryonic development. Our system reproducibly captures spontaneous differentiation and co-development of embryonic epiblast-like and extra-embryonic hypoblast-like lineages, establishes key signalling hubs with secreted modulators and undergoes symmetry breaking-like events. Single-cell transcriptomics confirms differentiation into diverse cell states of the perigastrulating human embryo14,15 without establishing placental cell types, including signatures of post-implantation epiblast, amniotic ectoderm, primitive streak, mesoderm, early extra-embryonic endoderm, as well as initial yolk sac induction. Collectively, our system captures key features of human embryonic development spanning from Carnegie stage16 4–7, offering a reproducible, tractable and scalable experimental platform to understand the basic cellular and molecular mechanisms that underlie human development, including new opportunities to dissect congenital pathologies with high throughput

Molecular characterization of Left-Right symmetry breaking in the mouse embryo

ABSTRACT The asymmetric morphology of the mammalian heart is essential to its function as the organ of pulmonary and systemic double circulation. Left-right asymmetry is established by a leftward flow in the node that results in the asymmetric expression of Nodal . This triggers a cascade of asymmetric expression of downstream genes, such as Pitx2c , in the lateral plate mesoderm that gives rise to the first morphologically recognizable primordial heart structure, the cardiac crescent. Relatively little is known about gene expression asymmetries in the cardiac crescent that might underpin asymmetric cardiac morphogenesis. To systematically identify asymmetrically expressed genes, we performed a single-cell transcriptional analysis of manually dissected left and right halves of the cardiac crescent at stages spanning symmetry breaking. This revealed both left and right-sided genes that have not previously been implicated in left-right symmetry breaking. Some of these were expressed in multiple cell types but showed asymmetric expression in only a sub-set of cell types. We validated these findings using multiplexed in situ Hybridization Chain Reaction (HCR) and high-resolution volume imaging to characterize the expression patterns of select genes. Using Dnah iv/iv mutant embryos that show randomized situs, we established that all the genes tested tracked the asymmetric expression of Pitx2c , indicating their asymmetric expression also arose from the early asymmetries at the node. This study provides a high-fidelity molecular characterization of left-right symmetry breaking during cardiac crescent formation, providing a basis for future mechanistic studies on asymmetric cardiac morphogenesis

Floristic compositions and physiognomy aspects of plant in river-bay of Igarapés riacho doce, lages and onça, located in the city of President Figueiredo, state of Amazonas, Brasil

O objetivo deste trabalho foi estudar a composição florísticas das comunidades vegetais dos Igarapés Riacho Doce, Lajes e Igarapé da Onça do Município de Presidente Figueiredo, estado do Amazonas, Brasil, apresentando as estimativas dos números de espécies, famílias e indivíduos registrados numa área de 1 ha (parcelas de 10x1000m, alocadas aleatoriamente para cada comunidade vegetal). Nestas parcelas foram tomadas medidas de indivíduos com 10cm ou mais de diâmetro à altura do peito (D.A.P.), medidas as alturas do fuste (m), posição sociológica e qualidade do fuste. Analisou-se o índice de diversidade de Shannon e Weaver (H’), uniformidade ou equitabilidade, coeficiente de mistura e o índice de espécie raras, (IER). Os resultados encontrados mostram que, as famílias Fabaceae, Sapotaceae e Caesalpiniaceae, destacaram-se pela riqueza florística e dominância nas diferentes comunidades vegetais. As espécies mais abundantes que ocorreram nesses ambientes foram Sandwithia guyanensis, Pouteria sp. e Oenocarpus bataua. O Índice de Shannon- Weaver registrou valores bastante elevados nas três comunidades vegetais estudadas, a comunidade vegetal do Igarapé Riacho Doce, entretanto apresentou maior diversidade (3,67). De acordo com o coeficiente de mistura, as comunidades vegetais dos igarapés analisadas são similares entre [email protected] objective of this work was to study the floristic composition of plant communities of Igarapés Riacho Doce, Lajes and Onça of the city of President Figueiredo, state of Amazonas, Brazil. Estimates of the numbers of species, families and individuals registered in an area of one hectare (plots of 10x1000m, randomly allocated to each plant community) were presenting. In these plots measures were taken from individuals with 10 cm or more of diameter at breast height (DBH), heights of trunk (m), sociological position and trunk quality. It was examined the diversity index of shannon and Weaver (H‘), uniformity coefficient of mixture and the index of rare species. The results show that the families Fabaceae, sapotaceae and caesalpiniaceae, outstanding the number of species and dominance in the different plant communities. The most abundant species occurring in these environments were Sandwithia guyanensis, Pouteria sp. and Oenocarpus bataua. The index of shannon-Weaver recorded very high values in the three plant communities studied. However, the plant community of igarapé Riacho Doce presented greater diversity (3.67). According to the coeffi cient of mixture, the plant communities of the igarapés considered are similar to each other