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First published online April 30, 2004; 10.1104/pp.103.034900 Plant Physiology 135:266-278 (2004) © 2004 American Society of Plant Biologists Interactions between Auxin Transport and the Actin Cytoskeleton in Developmental Polarity of Fucus distichus Embryos in Response to Light and Gravity1Department of Biology, Wake Forest University, Winston-Salem, North Carolina 271097325
Land plants orient their growth relative to light and gravity through complex mechanisms that require auxin redistribution. Embryos of brown algae use similar environmental stimuli to orient their developmental polarity. These studies of the brown algae Fucus distichus examined whether auxin and auxin transport are also required during polarization in early embryos and to orient growth in already developed tissues. These embryos polarize with the gravity vector in the absence of a light cue. The auxin, indole-3-acetic acid (IAA), and auxin efflux inhibitors, such as naphthylphthalamic acid (NPA), reduced environmental polarization in response to gravity and light vectors. Young rhizoids are negatively phototropic, and NPA also inhibits rhizoid phototropism. The effect of IAA and NPA on gravity and photopolarization is maximal within 2.5 to 4.5 h after fertilization (AF). Over the first 6 h AF, auxin transport is relatively constant, suggesting that developmentally controlled sensitivity to auxin determines the narrow window during which NPA and IAA reduce environmental polarization. Actin patches were formed during the first hour AF and began to photolocalize within 3 h, coinciding with the time of NPA and IAA action. Treatment with NPA reduced the polar localization of actin patches but not patch formation. Latrunculin B prevented environmental polarization in a time frame that overlaps the formation of actin patches and IAA and NPA action. Latrunculin B also altered auxin transport. Together, these results indicate a role for auxin in the orientation of developmental polarity and suggest interactions between the actin cytoskeleton and auxin transport in F. distichus embryos.
1 This work was supported by the National Aeronautics and Space Administration (grant no. NAG21203 to G.K.M.) and the National Science Foundation (grant no. IBN9318250 to G.K.M.). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.034900. * Corresponding author; e-mail muday{at}wfu.edu; fax 3367585316. Received October 17, 2003; returned for revision March 15, 2004; accepted March 21, 2004. Related articles in Plant Physiol.:
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