Developmental and Structural Section
Lopez-Smith, Renee , Renzaglia, Karen S. .
Do land plant motile gametes possess outer dynein?
Among land plants, motile gametes are produced by bryophytes, ferns, Ginkgo and cycads. Although the number of flagella ranges from two to thousands per gamete, axonemal structure consisting of nine doublet microtubules surrounding a central pair complex (9+2 configuration) is highly conserved. It has been reported that motile sperm cells of archegoniates lack outer dynein arms, motor protein complexes that are typically associated with the A-tubule of doublet microtubules in axonemes. The lack of outer dynein has been suggested to be correlated with the inability of archegoniate sperm to swim backwards. We conducted a survey of 18 green plants (one alga, two liverworts, two mosses, four lycophytes, one hornwort, seven ferns and Ginkgo) for the presence of outer dynein in the flagella of pre-released sperm cells. Outer dynein arms are always visible in the green alga Chara and Isoetes, a lycophyte. Modified protocols that include tannic acid in the fixative enable the visualization of outer dynein in mosses and liverworts, which occur at a lower frequency than in other taxa. Peculiarities in land plant fertilization may be related to the observed differences in axonemal substructure as compared with green algae. In order to reach the egg, the sperm cells must navigate through the narrow archegonial neck canal before contacting the egg in the venter. The ability to swim backwardly might interfere with the successful movement through the neck canal. Similar swimming constraints do not apply to green algae in which backward swimming is the norm. This poster will explore the architecture of the archegonium as it relates to swimming behavior and the presence or absence of dynein in selected land plants and Chara sperm cells.
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1 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM