title: Multiflagellated sperm cells of Ceratopteris richardii are bathed in arabinogalactan proteins throughout development.
abstract: •
  
  
  OBJECTIVE
  Sperm cell differentiation in ferns involves the origin of an elaborate locomotory apparatus, including 70+ flagella, and the structural modification of every cellular component. Because arabinogalactan proteins (AGPs) are implicated in molecular signaling and in regulation of plant development, we speculated that these glycoproteins would be present during spermiogenesis in ferns.•
  
  
  METHODS
  Using β-glucosyl Yariv reagents that specifically bind to and inhibit AGPs and immunogold localizations with monoclonal antibodies JIM13, JIM8, and LM6, we examined the specific expression patterns of AGPs and inhibited their function during sperm cell development in the model fern Ceratopteris richardii.•
  
  
  RESULTS
  Developing sperm cells stained intensely with Yariv phenylglycosides, demonstrating the presence of AGPs. JIM13-AGP epitopes were widespread throughout development in the expanding extraprotoplasmic matrix (EPM) in which flagella elongate, cytoplasm is eliminated, and spherical spermatids become coiled. JIM8 and LM6 epitopes localized to the plasmalemma on growing flagella and on the rapidly changing sperm cell body. Spermatids treated with β-glucosyl lacked an EPM and formed fewer, randomly arranged flagella.•
  
  
  CONCLUSIONS
  We demonstrated that AGPs are abundant in the EPM and along the plasmalemma and that the three AGP epitopes have specific expression patterns during development. Coupled with inhibition studies, these results identify AGPs as critical to the formation of an extraprotoplasmic matrix and the consequent origin and development of flagella in an orderly and precise fashion around the cell. We speculate that AGPs may play additional roles as signaling molecules involved in cell shaping, cytoskeletal development, vesicle trafficking, and cytoplasmic elimination.
authors.affiliation: Department of Plant Biology, Southern Illinois University Carbondale, Carbondale, Illinois 62901 USA.
authors.forename: Renee A
authors.initials: RA
authors.lastname: Lopez
authors.affiliation: Department of Plant Biology, Southern Illinois University Carbondale, Carbondale, Illinois 62901 USA.
authors.forename: Karen S
authors.initials: KS
authors.lastname: Renzaglia
mesh_terms: D000939:Epitopes; D029624:Ferns / Q000254:growth & development / Q000378:metabolism*; D005407:Flagella / Q000378:metabolism*; D005960:Glucosides; D006023:Glycoproteins / Q000378:metabolism*; D009088:Mucoproteins / Q000378:metabolism*; D010696:Phloroglucinol / Q000031:analogs & derivatives; D010940:Plant Proteins / Q000378:metabolism; D011058:Pollen / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000939:Epitopes; D005960:Glucosides; D006023:Glycoproteins; D009088:Mucoproteins; D010940:Plant Proteins; C104977:Yariv reagent; C006619:arabinogalactan proteins; D010696:Phloroglucinol
keywords: AGPs; Ceratopteris; Yariv reagent; cellular differentiation; extraprotoplasmic matrix; flagella; immunolocalization; spermatozoid