ON  THE  COVER   
 Vol. 70  No4  December 2005
 Technical note 

Dynamics of the plant Aurora kinase AtAUR3 during mitosis and spindle abnormality induced by AtAUR3 overexpression

    Aurora kinase has been first identified in a Drosophila mutant for defects of the mitotic spindle in 1995, Its nominal origin is the phenotype of monopolar spindles similar to Northern lights. Aurora borealis. Three Aurora kinase orthologs, AtAUR1, AtAUR2 and AtAUR3, were identified in Arabidopsis thaliana. Subcellular localization of AtAUR3 fused with GFP in tobacco BY-2 cultured cells dynamically changes during mitosis starting from the top (prophase) in clockwise manner of the cover photograph. AtAUR3 localized in the cytoplasm around the nucleus during interphase. At prophase,the dot-like condensed signals of AtAUR3 appeared when the chromosomes began to condense. At prometaphase, the signals moved to the equatorial plate along with the condensed chromosomes. At metaphase, the signals align in the center of the metaphase plates (bottom). However, at anaphase, in accordance with chromosome separation, AtAUR3 signals were almost ubiquitously observed on the whole chromosome. After cell division, the AtAUR3 signal returned to the nuclear membrane and the cytoplasm around the nucleus. The localization pattern of AtAUR3 from prophase to anaphase is very similar to that of phosphorylated serine 10 of histone H3. Overexpression of AtAUR3 induces defects of the mitotic spindle. One of the phenotype is a fig-like spindle as shown in the center of the cover photography. The fluorescent image was an AtAUR3-overexpressed tobacco cell at metaphase by immunostaining with anti--tubulin (in green) or -tubulin (in red) antibodies and staining with DAPI in blue. The fig-like spindle is spread at one side like a monopolar spindle. A few deviations of -tubulin from the spindle were observed with the one-sided distribution of -tubulin. This suggests that AtAUR3 function in microtubule assembly through mitotic spindle formation. (See Kawabe A. et al. 2005: Plant Mol. Biol. 58, 1-13).

    (Sachihiro Matsunaga1, Daisuke Kurihara1, Akira Kawabe1, Katsuyuki Nakagawa1, Arata Yoneda2, Seiichiro Hasezawa2, Susumu Uchiyamal and Kiichi Fukui1 Department of Biotechnology. Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita Osaka 565-0871 , Japan, 2 Department of Integrated Biosciences. Graduate School of Frontier Sciences, University of Tokyo, FSB-701, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan) 


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