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Abstract Detail


Pteridological Section/AFS

Johnson, Gabriel [1], Renzaglia, Karen S. [1].

Distributional changes of cell wall polysaccharides during placental development in Ceratopteris richardii.

The distributions of cell wall polysaccharide epitopes were monitored in the sporophyte-gametophyte junction at three stages of embryogenesis in Ceratopteris richardii. This is the first immunolocalization study performed on transfer cells in a pteridophyte. Monoclonal antibodies were used to label different motifs of homogalacturonic acid pectins (HGAs), rhamnogalacturonan I pectins (RG-Is), and arabinogalactan proteins (AGPs) at the light and electron microscope levels. During the initial formative divisions that define organ apical cells, all cells have similar pectin and AGP content. Gametophyte cells only label for AGPs at the surfaces adjacent to the embryo. As the placental foot cells differentiate, they form cell wall ingrowths that label with JIM5 but not JIM7. This indicates the HGAs became methyl de-esterified. At this stage, the remainder of the embryo and gametophyte label with JIM7 for methyl esterified HGAs. Throughout ingrowth formation, cellulose is localized by cellobiohydrolase II. Accordingly, fucosylated xyloglucan hemicelluloses that stain with the CCRC-M1 antibody form a labeling gradient that increases toward the root apical cell. After labyrinths of wall ingrowths form on both generations of the placenta, AGP epitopes are identified with LM6, LM2, and JIM8 antibodies. Labeling in older embryos that have formed several leaves and roots suggest AGP expression increases over time in gametophytic placental cells while decreasing in the sporophyte cells. As in other pteridophytes, no C. richardii tissue labels with LM5 for RG-I galactan side-chains. These results suggest AGPs play a role in cell differentiation and wall expansion during placental development.


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1 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA

Keywords:
Ceratopteris richardii
Cell wall deposition
Arabinogalactan-protein
Placenta
Immunolocalization
Pectin.

Presentation Type: Oral Paper:Papers for Sections
Session: CP20
Location: Lake Michigan/Hilton
Date: Monday, July 9th, 2007
Time: 2:15 PM
Number: CP20014
Abstract ID:1631


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