Flagellar apparatus ultrastructure inMesostigma viride (Prasinophyceae)
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- Melkonian, M. Plant Syst Evol (1989) 164: 93. doi:10.1007/BF00940432
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The ultrastructure of the flagellar apparatus ofMesostigma virideLauterborn (Prasinophyceae) has been studied in detail with particular reference to absolute configurations, numbering of basal bodies, basal body triplets and flagellar roots. The two basal bodies are interconnected by three connecting fibers (one distal fiber = synistosome, and two proximal fibers). The flagellar apparatus shows 180° rotational symmetry; four microtubular flagellar roots and two system II fibers are present. The microtubular roots represent a 4-6-4-6-system. The left roots (1s, 2s) consist of 4 microtubules, each with the usual 3 over 1 root tubule pattern. Each right root (1d, 2d) is proximally associated with a small, but typical multi-layered structure (MLS). The latter displays several layers corresponding to the S1 (the spline microtubules: 5–7), and presumably the S2—S4 (the lamellate layers) of the MLS of theCharophyceae. At its proximal origin (near the basal bodies) each right root originates with only two microtubules, the other spline microtubules being added more distally. The structural and positional information obtained in this study strongly suggest that one of the right roots (1d) ofMesostigma is homologous to the MLS-root of theCharophyceae and sperm cells of archegoniate land plants. Thus the typical cruciate flagellar root system of the green algae and the “unilateral” flagellar root system of theCharophyceae and archegoniates share a common ancestry. Some functional and phylogenetic aspects of MLS-roots are discussed.