Flagellar Root-Mediated Interactions Between the Flagellar Apparatus and Cell Organelles in Green Algae

Abstract

The flagellar apparatus is a structurally and biochemically complex cell organelle, but it is not a separate compartment in the sense of Schnepf (this vol.). It is a local specialization of the cytoplasmic compartment involving a microtubular organelle (the axoneme), its associated basal apparatus and the ensheathing plasma membrane plus cell surface components. There is exchange of metabolites, macromolecules and ATP into and out of the flagellar apparatus without requiring passage through a membrane, therefore also in functional terms the flagellar apparatus is not a separate compartment. It nevertheless maintains structural and functional integrity and therefore qualifies as an important eukaryotic cell organelle. There is good evidence that passage of ribosomes into the free flagellum does not occur, although in some green algal taxa ribosomes may be found consistently inside the basal bodies (e.g., Melkonian and Berns 1983). The flagellar membrane is also specific and does not mix with other areas of the plasma membrane (review by Bloodgood 1982). The same holds true for cell surface components of the flagellar membrane (sexual agglutinin of green algal gametes, flagellar hairs and scales; Adair et al. 1983, Melkonian 1984). How lateral diffusion of integral membrane proteins from the flagellar membrane into other areas of the plasma membrane is prevented, is unknown, but the flagellar membrane covering the transition zone may be such a lateral diffusion barrier, since it is not susceptible to low concentrations of nonionic detergents unlike the rest of the flagellar membrane (Goodenough 1983).KeywordsNuclear EnvelopeBasal BodyCell OrganelleMotile CellContractile VacuoleThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.