title: Hydroxyproline O-arabinosyltransferase mutants oppositely alter tip growth in Arabidopsis thaliana and Physcomitrella patens.
abstract: Hydroxyproline O-arabinosyltransferases (HPATs) are members of a small, deeply conserved family of plant-specific glycosyltransferases that add arabinose sugars to diverse proteins including cell wall-associated extensins and small signaling peptides. Recent genetic studies in flowering plants suggest that different HPAT homologs have been co-opted to function in diverse species-specific developmental contexts. However, nothing is known about the roles of HPATs in basal plants. We show that complete loss of HPAT function in Arabidopsis thaliana and the moss Physcomitrella patens results in a shared defect in gametophytic tip cell growth. Arabidopsis hpat1/2/3 triple knockout mutants suffer from a strong male sterility defect as a consequence of pollen tubes that fail to fully elongate following pollination. Knocking out the two HPAT genes of Physcomitrella results in larger multicellular filamentous networks due to increased elongation of protonemal tip cells. Physcomitrella hpat mutants lack cell-wall associated hydroxyproline arabinosides and can be rescued with exogenous cellulose, while global expression profiling shows that cell wall-associated genes are severely misexpressed, implicating a defect in cell wall formation during tip growth. Our findings point to a major role for HPATs in influencing cell elongation during tip growth in plants.
authors.affiliation: Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11746, USA.
authors.forename: Cora A
authors.initials: CA
authors.lastname: MacAlister
authors.affiliation: Instituto Gulbenkian de Ciência, P-2780-156, Oeiras, Portugal.
authors.forename: Carlos
authors.initials: C
authors.lastname: Ortiz-Ramírez
authors.affiliation: Instituto Gulbenkian de Ciência, P-2780-156, Oeiras, Portugal.
authors.forename: Jörg D
authors.initials: JD
authors.lastname: Becker
authors.affiliation: Instituto Gulbenkian de Ciência, P-2780-156, Oeiras, Portugal.|Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, 20742-5815, USA.
authors.forename: José A
authors.initials: JA
authors.lastname: Feijó
authors.affiliation: Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11746, USA.|Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11746, USA.
authors.forename: Zachary B
authors.initials: ZB
authors.lastname: Lippman
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D019068:Bryopsida / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D006909:Hydroxyproline / Q000378:metabolism; D010430:Pentosyltransferases / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D010430:Pentosyltransferases; C101967:arabinosyltransferase; D006909:Hydroxyproline
keywords: Arabidopsis thaliana; Physcomitrella patens; arabinosylation; cell wall; development; extensins; glycosylation; pollination; protonema; tip growth