Basal body replication in green algae - when and where does it start?

Basal body duplication in the green alga Spermatozopsis similis was reinves tigated using GT335, an antibody binding to polyglutamylated tubulins, and antibodies directed to p210, a component of the flagellar transition region which represents the distal border of the basal body. p210 was also detect ed in small spots at the base of each basal body which increased in size pr ior to mitosis. The presence of p210 on one of the microtubular flagellar r oots suggested a transport of basal body material along these tracks. Immun ogold electron microscopy confirmed the presence of p210 in the probasal bo dies. Further, small probasal bodies are apparently connected to the mature basal bodies by centrin fibers as observed after artificially induced basa l body separation in Xenopus egg extract. While basal bodies grew, most of the p210 remained at the tip of elongating basal bodies, but two or four ad ditional spots were observed in distinct patterns near the base of the basa l bodies. In cytokinesis, basal body pairs separated and p210 was observed in a strong signal at the tip and a weaker one in the vicinity of the proxi mal end of each basal body. We interpret the data as indicating that a new p210-containing structure forms near the proximal end of the basal bodies d uring basal body elongation, representing the precursor of the next generat ion of basal bodies. Thus, basal bodies appear to seed the succeeding gener ation already during their own development, a mechanism which could ensure the correct number and position of basal bodies.