SF-ASSEMBLIN IN CHLAMYDOMONAS - SEQUENCE CONSERVATION AND LOCALIZATION DURING THE CELL-CYCLE

Previously, SF-assemblin has been identified as the filament-forming c omponent of the striated microtubule-associated fibers (SMAFs), which emerge from the basal bodies in several green flagellates. We have seq uenced cDNAs coding for SF-assemblin from Chlamydomonas reinhardtii an d C. eugametos. Comparison of the deduced amino acid sequences with th e previously described green algal SF-assemblins shows identities betw een 54 and 71%, indicating a strong drift in sequence. Cells of C. rei nhardtii were analyzed by double immunofluorescence using polyclonal a nti-SF-assemblin and anti-alpha-tubulin. In interphase cells, SF-assem blin is associated with all four microtubular flagellar roots. During mitosis the SF-assemblin-based cytoskeleton is reorganized; it divides in prophase and is reduced to two dot-like structures at each spindle pole in metaphase. During anaphase, the two dots present at each pole are connected again. In telophase we observed an asymmetrical outgrow th of new fibers. These observations suggest a role for SF-assemblin i n reestablishing the microtubular root system characteristic of interp hase cells after mitosis. (C) 1997 Wiley-Liss, Inc.