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First published online May 27, 2005; 10.1104/pp.104.055665 Plant Physiology 138:1071-1082 (2005) © 2005 American Society of Plant Biologists Cloning and Functional Characterization of a Formin-Like Protein (AtFH8) from Arabidopsis1Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, and College of Life Science, Beijing Normal University, Beijing 100875, People's Republic of China
The actin cytoskeleton is required for many cellular processes in plant cells. The nucleation process is the rate-limiting step for actin assembly. Formins belong to a new class of conserved actin nucleator, which includes at least 2 formin homology domains, FH1 and FH2, which direct the assembly of unbranched actin filaments. The function of plant formins is quite poorly understood. Here, we provide the first biochemical study of the function of conserved domains of a formin-like protein (AtFH8) from Arabidopsis (Arabidopsis thaliana). The purified recombinant AtFH8(FH1FH2) domain has the ability to nucleate actin filaments in vitro at the barbed end and caps the barbed end of actin filaments, decreasing the rate of subunit addition and dissociation. In addition, purified AtFH8(FH1FH2) binds actin filaments and severs them into short fragments. The proline-rich domain (FH1) of the AtFH8 binds directly to profilin and is necessary for nucleation when actin monomers are profilin bound. However, profilin inhibits the nucleation mediated by AtFH8(FH1FH2) to some extent, but increases the rate of actin filament elongation in the presence of AtFH8(FH1FH2). Moreover, overexpression of the full-length AtFH8 in Arabidopsis causes a prominent change in root hair cell development and its actin organization, indicating the involvement of AtFH8 in polarized cell growth through the actin cytoskeleton.
1 This work was supported by the National Science Foundation for Distinguished Young Scholars (grant no. 30325005 to H.R.) and the National Natural Science Foundation of China (grant no. 30470176 to H.R.). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.055665. * Corresponding author; e-mail hren{at}bnu.edu.cn; fax 861058807721. Received October 26, 2004; returned for revision January 5, 2005; accepted January 24, 2005. Related articles in Plant Physiol.:
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