title: The Physcomitrella patens exocyst subunit EXO70.3d has distinct roles in growth and development, and is essential for completion of the moss life cycle.
abstract: The exocyst, an evolutionarily conserved secretory vesicle-tethering complex, spatially controls exocytosis and membrane turnover in fungi, metazoans and plants. The exocyst subunit EXO70 exists in multiple paralogs in land plants, forming three conserved clades with assumed distinct roles. Here we report functional analysis of the first moss exocyst subunit to be studied, Physcomitrella patens PpEXO70.3d (Pp1s97_91V6), from the, as yet, poorly characterized EXO70.3 clade. Following phylogenetic analysis to confirm the presence of three ancestral land plant EXO70 clades outside angiosperms, we prepared and phenotypically characterized loss-of-function Ppexo70.3d mutants and localized PpEXO70.3d in vivo using green fluorescent protein-tagged protein expression. Disruption of PpEXO70.3d caused pleiotropic cell elongation and differentiation defects in protonemata, altered response towards exogenous auxin, increased endogenous IAA concentrations, along with defects in bud and gametophore development. During mid-archegonia development, an abnormal egg cell is formed and subsequently collapses, resulting in mutant sterility. Mutants exhibited altered cell wall and cuticle deposition, as well as compromised cytokinesis, consistent with the protein localization to the cell plate. Despite some functional redundancy allowing survival of moss lacking PpEXO70.3d, this subunit has an essential role in the moss life cycle, indicating sub-functionalization within the moss EXO70 family.
authors.affiliation: Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná 5, 128 44, Prague 2, Czech Republic.|Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02, Prague 6, Czech Republic.
authors.forename: Anamika
authors.initials: A
authors.lastname: Rawat
authors.affiliation: Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná 5, 128 44, Prague 2, Czech Republic.|Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02, Prague 6, Czech Republic.
authors.forename: Lucie
authors.initials: L
authors.lastname: Brejšková
authors.affiliation: Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná 5, 128 44, Prague 2, Czech Republic.|Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02, Prague 6, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Hála
authors.affiliation: Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná 5, 128 44, Prague 2, Czech Republic.
authors.forename: Fatima
authors.initials: F
authors.lastname: Cvrčková
authors.affiliation: Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná 5, 128 44, Prague 2, Czech Republic.|Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02, Prague 6, Czech Republic.
authors.forename: Viktor
authors.initials: V
authors.lastname: Žárský
mesh_terms: D019068:Bryopsida / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism* / Q000648:ultrastructure; D002454:Cell Differentiation; D049109:Cell Proliferation; D048749:Cytokinesis; D055786:Gene Knockout Techniques; D058685:Genetic Pleiotropy; D006112:Gravitation; D016013:Likelihood Functions; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D019441:Plant Epidermis / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D011523:Protoplasts / Q000378:metabolism; D012038:Regeneration
chemical_list: D010940:Plant Proteins
keywords: EXO70; Physcomitrella patens; auxin; cytokinesis; egg cell development; exocyst; phylogeny; secretory pathway