Roots1

ABSTRACT Many unicellular eukaryotic organisms possess complex fiber systems that organize and anchor the flagellar basal apparatus in the cell 20, 24]. In 1978 we first published the observation that one of these fiber systems, the striated flagellar root of the quadriflagellate green alga Tetraselmis subcordiformis (=Platymonas subcordiformis), is a contractile organelle 31]. We subsequently found that striated flagellar roots are composed, in part, of the Ca²⁺-binding protein centrin 30]. Since that time, centrin has been found to be a ubiquitous component of the flagellar basal apparatus, basal bodies and centrioles, and centrosomes and mitotic spindle poles of eukaryotic cells (for general reviews see 28, 34]). While we have learned a great deal about centrin from other organisms, our earliest success in understanding the biology of centrin was in large part due to the extraordinary extent to which Tetraselmis cells have elaborated their centrin-based organelles. In this paper, I will return attention to several unanswered questions concerning Tetraselmis striated flagellar root behavior and I will suggest several new directions that students may wish to pursue in order to tease fresh insights from this fascinating organism.