Strategies of 3-D growth in brown algae

ongoing

ALTER e-GROW aims to identify the mechanisms underlying the development of tri-dimensional (3D) tissues in multicellular organisms. Many physical factors influence the shape of an organism growing from a single cell or a small group of cells: the direction of growth along the x, y and z axis; when and how rapidly growth occurs, and whether the region of growth is diffuse or localised. An almost infinite number of combinations of these factors are possible. Most animals and land plants grow in 3D from the onset of embryogenesis. Other multicellular organisms, however, grow in 3D later in their development; for example, by emergence of a 3D bud from a single row of cells (as in mosses) or by aggregation of hyphae (as in fungi). The large phylogenetic distances between current model organisms complicate the investigation of the mechanisms underlying this diversity of 3D growth strategies. Brown algae, by contrast, display all of these 3D growth modes in a single clade, making them a unique subject for investigation of the mechanisms. Moreover, their independent and recent evolution when compared to the other clades suggests that they have developed divergent 3D growth mechanisms. In this project, my team will observe and quantify parameters of 3D growth in four species of brown algae, each representative of one of the main types of 3D growth mechanisms also found in animals, plants and Fungi. Then we will build dynamic mathematical models that describe these mechanisms by integrating quantitative data on cell shape, cell wall thickness and stiffness, cytoskeleton organisation, turgor and cell–cell tension in dynamic 3D growth simulations, and test them by comparing the 3D growth pattern of wild type algae and genetic mutants. Thus, this project will pioneer what is currently a ‘black box’ of knowledge about the development of brown algae, examining how these organisms raise multicellular structures in 3D space.