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Proc Natl Acad Sci U S A. 2016 Dec 6;113(49):14157-14162. Epub 2016 Nov 22.

Cytoskeleton dynamics control the first asymmetric cell division in Arabidopsis zygote.

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Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan.
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8562, Japan.
Gregor Mendel Institute, Vienna Biocenter, Austrian Academy of Sciences, 1030 Vienna, Austria.
Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546.
Japan Science and Technology Agency, Exploratory Research for Advanced Technology Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan.
Institute of Transformative Bio-Molecules, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan.
Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan;


The asymmetric cell division of the zygote is the initial and crucial developmental step in most multicellular organisms. In flowering plants, whether zygote polarity is inherited from the preexisting organization in the egg cell or reestablished after fertilization has remained elusive. How dynamically the intracellular organization is generated during zygote polarization is also unknown. Here, we used a live-cell imaging system with Arabidopsis zygotes to visualize the dynamics of the major elements of the cytoskeleton, microtubules (MTs), and actin filaments (F-actins), during the entire process of zygote polarization. By combining image analysis and pharmacological experiments using specific inhibitors of the cytoskeleton, we found features related to zygote polarization. The preexisting alignment of MTs and F-actin in the egg cell is lost on fertilization. Then, MTs organize into a transverse ring defining the zygote subapical region and driving cell outgrowth in the apical direction. F-actin forms an apical cap and longitudinal arrays and is required to position the nucleus to the apical region of the zygote, setting the plane of the first asymmetrical division. Our findings show that, in flowering plants, the preexisting cytoskeletal patterns in the egg cell are lost on fertilization and that the zygote reorients the cytoskeletons to perform directional cell elongation and polar nuclear migration.


Arabidopsis thaliana; actin filament; apical–basal axis; microtubule; zygote polarity

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