Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome.

The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP

Fibronectin fibrillogenesis regulates three-dimensional neovessel formation

During vasculogenesis and angiogenesis, endothelial cell responses to growth factors are modulated by the compositional and mechanical properties of a surrounding three-dimensional (3D) extracellular matrix (ECM) that is dominated by either cross-linked fibrin or type I collagen. While 3D-embedded endothelial cells establish adhesive interactions with surrounding ligands to optimally respond to soluble or matrix-bound agonists, the manner in which a randomly ordered ECM with diverse physico-mechanical properties is remodeled to support blood vessel formation has remained undefined. Herein, we demonstrate that endothelial cells initiate neovascularization by unfolding soluble fibronectin (Fn) and depositing a pericellular network of fibrils that serve to support cytoskeletal organization, actomyosin-dependent tension, and the viscoelastic properties of the embedded cells in a 3D-specific fashion. These results advance a new model wherein Fn polymerization serves as a structural scaffolding that displays adhesive ligands on a mechanically ideal substratum for promoting neovessel development

Virtual Seminar on the Bioapparatus

Includes a text based on transcripts of proceedings of a seminar on the "bioapparatus," conceived as the focus of issues concerning technology and the body. Statements by 20 artists and writers treat such topics as natural artifice, designing the social, virtual reality, art machines, and aural/visual space. Biographical notes on the participants