In: Cytoskeleton: Cell Movement... ISBN: 978-1-60876-559-1 Editors: S. Lansing et al., pp. 205-218 © 2010 Nova Science Publishers, Inc. Chapter VII Migrating Plant Cell: F-Actin Asymmetry Directed by Phosphoinositide Signaling Koji Mikami * Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate 041-8611, Japan. Abstract Polarity is a fundamental cell property essential for differentiation, proliferation and morphogenesis in unicellular and multicellular organisms. It is well known that polarized distribution of F-actin is important in providing the driving force for directional migration in mammalian leukocytes and Dictyostelium cells. Phosphoinositide (PI) signaling, including phosphatidylinositol kinases and phospholipases, is also critical for the formation of cell polarity in these cells. A monospore from the marine red alga Porphyra yezoensis is well known as a migrating plant cell and thus is a unique and useful material for investigating polarity determination in plant cells. As in leukocytes and Dictyostelium cells, monospore migration requires asymmetrical distribution of F-actin, whose establishment is regulated by the phosphatidylinositol 3-kinase and phospholipase C, whereas * Corresponding author: Tel/Fax: +81-138-40-8899; E-mail: komikami@fish.hokudai.ac.jp