title: Electrophoretic profiling and immunocytochemical detection of pectins and arabinogalactan proteins in olive pollen during germination and pollen tube growth.
abstract: OBJECTIVE
  Cell wall pectins and arabinogalactan proteins (AGPs) are important for pollen tube growth. The aim of this work was to study the temporal and spatial dynamics of these compounds in olive pollen during germination.
  
  
  METHODS
  Immunoblot profiling analyses combined with confocal and transmission electron microscopy immunocytochemical detection techniques were carried out using four anti-pectin (JIM7, JIM5, LM5 and LM6) and two anti-AGP (JIM13 and JIM14) monoclonal antibodies.
  
  
  RESULTS
  Pectin and AGP levels increased during olive pollen in vitro germination. (1 → 4)-β-d-Galactans localized in the cytoplasm of the vegetative cell, the pollen wall and the apertural intine. After the pollen tube emerged, galactans localized in the pollen tube wall, particularly at the tip, and formed a collar-like structure around the germinative aperture. (1 → 5)-α-l-Arabinans were mainly present in the pollen tube cell wall, forming characteristic ring-shaped deposits at regular intervals in the sub-apical zone. As expected, the pollen tube wall was rich in highly esterified pectic compounds at the apex, while the cell wall mainly contained de-esterified pectins in the shank. The wall of the generative cell was specifically labelled with arabinans, highly methyl-esterified homogalacturonans and JIM13 epitopes. In addition, the extracellular material that coated the outer exine layer was rich in arabinans, de-esterified pectins and JIM13 epitopes.
  
  
  CONCLUSIONS
  Pectins and AGPs are newly synthesized in the pollen tube during pollen germination. The synthesis and secretion of these compounds are temporally and spatially regulated. Galactans might provide mechanical stability to the pollen tube, reinforcing those regions that are particularly sensitive to tension stress (the pollen tube-pollen grain joint site) and mechanical damage (the tip). Arabinans and AGPs might be important in recognition and adhesion phenomena of the pollen tube and the stylar transmitting cells, as well as the egg and sperm cells.
authors.affiliation: Departament of Biochemistry, Cell and Molecular Biology of Plants, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Profesor Albareda 1, 18008, Granada, Spain. antoniojesus.castro@eez.csic.es
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Castro
authors.forename: Cynthia
authors.initials: C
authors.lastname: Suárez
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Zienkiewicz
authors.forename: Juan de Dios
authors.initials: Jde D
authors.lastname: Alché
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Zienkiewicz
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Rodríguez-García
mesh_terms: D004586:Electrophoresis / Q000379:methods; D005685:Galactans / Q000378:metabolism*; D018525:Germination; D007150:Immunohistochemistry / Q000379:methods; D046529:Microscopy, Electron, Transmission; D031658:Olea / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D010368:Pectins / Q000378:metabolism*; D053205:Pollen Tube / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D005685:Galactans; D010368:Pectins; C005653:arabinogalactan
keywords: Olea europaea; arabinogalactan protein; cell wall; pectin; pollen; pollen tube