title: Phosphatidylinositol 3-kinase activity and asymmetrical accumulation of F-actin are necessary for establishment of cell polarity in the early development of monospores from the marine red alga Porphyra yezoensis.
abstract: The polarized distribution of F-actin is important in providing the driving force for directional migration in mammalian leukocytes and Dictyostelium cells, in which compartmentation of phosphatidylinositol 3-kinase (PI3K) and phosphatidylinositol phosphatase is critical for the establishment of cell polarity. Since monospores from the red alga Porphyra yezoensis are a real example of migrating plant cells, the involvement of the cytoskeleton and PI3K was investigated during their early development. Our results indicate that the asymmetrical localization of F-actin at the leading edge is fixed by the establishment of the anterior-posterior axis in migrating monospores, which is PI3K-dependent and protein synthesis-independent. After migration, monospores adhere to the substratum and then become upright, developing into multicellular thalli via the establishment of the apical-basal axis. In this process, F-actin usually accumulates at the bottom of the basal cell and development after migration requires new protein synthesis. These findings suggest that the establishment of anterior-posterior and apical-basal axes are differentially regulated during the early development of monospores. Our results also indicate that PI3K-dependent F-actin asymmetry is evolutionally conserved in relation to the establishment of cell polarity in migrating eukaryotic cells.
authors.affiliation: Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate 041-8611, Japan.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: Naotsune
authors.initials: N
authors.lastname: Saga
authors.forename: Koji
authors.initials: K
authors.lastname: Mikami
mesh_terms: D000199:Actins / Q000378:metabolism*; D020418:Algal Proteins / Q000378:metabolism*; D002465:Cell Movement; D016764:Cell Polarity; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D044664:Porphyra / Q000201:enzymology / Q000254:growth & development* / Q000502:physiology; D021381:Protein Transport; D012623:Seawater; D013170:Spores / Q000201:enzymology / Q000254:growth & development* / Q000502:physiology
chemical_list: D000199:Actins; D020418:Algal Proteins; D019869:Phosphatidylinositol 3-Kinases