title: Three ancient hormonal cues co-ordinate shoot branching in a moss.
abstract: Shoot branching is a primary contributor to plant architecture, evolving independently in flowering plant sporophytes and moss gametophytes. Mechanistic understanding of branching is largely limited to flowering plants such as Arabidopsis, which have a recent evolutionary origin. We show that in gametophytic shoots of Physcomitrella, lateral branches arise by re-specification of epidermal cells into branch initials. A simple model co-ordinating the activity of leafy shoot tips can account for branching patterns, and three known and ancient hormonal regulators of sporophytic branching interact to generate the branching pattern- auxin, cytokinin and strigolactone. The mode of auxin transport required in branch patterning is a key divergence point from known sporophytic pathways. Although PIN-mediated basipetal auxin transport regulates branching patterns in flowering plants, this is not so in Physcomitrella, where bi-directional transport is required to generate realistic branching patterns. Experiments with callose synthesis inhibitors suggest plasmodesmal connectivity as a potential mechanism for transport.
authors: Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom.
authors: Yoan
authors: Y
authors: Coudert
authors: Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom.
authors: Wojtek
authors: W
authors: Palubicki
authors: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Umeå University, Umeå, Sweden.
authors: Karin
authors: http://orcid.org/0000-0003-2901-189X
authors: K
authors: Ljung
authors: Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University and Institute of Experimental Botany ASCR, Olomouc, Czech Republic.
authors: Ondrej
authors: O
authors: Novak
authors: Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom.
authors: Ottoline
authors: O
authors: Leyser
authors: Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom.
authors: C Jill
authors: CJ
authors: Harrison
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D019521:Body Patterning / Q000187:drug effects; D019068:Bryopsida / Q000187:drug effects / Q000254:growth & development*; D003583:Cytokinins / Q000096:biosynthesis; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007210:Indoleacetic Acids / Q000378:metabolism / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology; D008954:Models, Biological; D009024:Morphogenesis / Q000187:drug effects*; D009154:Mutation / Q000235:genetics; D019441:Plant Epidermis / Q000166:cytology / Q000254:growth & development; D010937:Plant Growth Regulators / Q000494:pharmacology*; D010940:Plant Proteins / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development*; D030821:Plants, Genetically Modified
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D007783:Lactones; D010937:Plant Growth Regulators; D010940:Plant Proteins
keywords: Physcomitrella; apical dominance; branching; developmental biology; gametophyte; plant biology; stem cells