n nnnCytoplasmic actin cables are the most prominent actin structuresin plant cells, but the molecular mechanism underlying theirformation is unknown. The function of these actin cables, whichare proposed to modulate cytoplasmic streaming and intracellularmovement of many organelles in plants, has not been studiedby genetic means. Here, we show that Arabidopsis thaliana formin3(AFH3) is an actin nucleation factor responsible for the formationof longitudinal actin cables in pollen tubes. The ArabidopsisAFH3 gene encodes a 785–amino acid polypeptide, whichcontains a formin homology 1 (FH1) and a FH2 domain. In vitroanalysis revealed that the AFH3 FH1FH2 domains interact withthe barbed end of actin filaments and have actin nucleationactivity in the presence of G-actin or G actin-profilin. Overexpressionof AFH3 in tobacco (Nicotiana tabacum) pollen tubes inducedexcessive actin cables, which extended into the tubes' apices.Specific downregulation of AFH3 eliminated actin cables in Arabidopsispollen tubes and reduced the level of actin polymers in pollengrains. This led to the disruption of the reverse fountain streamingpattern in pollen tubes, confirming a role for actin cablesin the regulation of cytoplasmic streaming. Furthermore, thesetubes became wide and short and swelled at their tips, suggestingthat actin cables may regulate growth polarity in pollen tubes.Thus, AFH3 regulates the formation of actin cables, which areimportant for cytoplasmic streaming and polarized growth inpollen tubes.展开▼
机译：ABSTRACTn n
n TOP n <字体颜色= 464c53>抽象 n 介绍 n 结果 n 讨论 n 方法 n 参考文献 n n nnn胞质肌动蛋白电缆是最突出的肌动蛋白结构 植物细胞，但 形成的分子机制尚不清楚。这些 被用来调节植物中许多细胞器的细胞质流和细胞内 运动的肌动蛋白电缆的功能，尚未通过遗传研究 。手段。在这里，我们显示拟南芥 formin3 （AFH3）是肌动蛋白成核因子，负责花粉管中纵向肌动蛋白电缆的形成 。 拟南芥 AFH3 基因编码一个785位氨基酸的多肽，该多肽 包含一个Formin同源性1（FH1）和一个FH2结构域。体外 分析显示，AFH3 FH1FH2结构域与肌动蛋白丝的倒刺端相互作用，在肌动蛋白存在的情况下具有肌动蛋白成核 活性。或G肌动蛋白-profilin。烟草花粉管中AFH3的过度表达 导致 肌动蛋白电缆过多，并延伸到管的顶点。 AFH3的特定下调消除了拟南芥 花粉管中的肌动蛋白电缆，并降低了花粉 颗粒中肌动蛋白的含量。这导致花粉管中反向喷泉流 模式的破坏，证实了肌动蛋白电缆 在细胞质流调节中的作用。此外，这些 管变宽，变短并在其尖端膨胀，表明 肌动蛋白电缆可能调节花粉管中的生长极性。 因此，AFH3调节肌动蛋白电缆的形成，肌动蛋白电缆对于 花粉管中的细胞质流和极化生长而言非常重要。展开▼
College of Biological Science, China Agricultural University, Beijing 100193, China|China Agricultural University-University of California-Riverside Joint Center for Biological Sciences and Biotechnology, China Agricultural University, Beijing 100193, China;
Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
China Agricultural University-University of California-Riverside Joint Center for Biological Sciences and Biotechnology, China Agricultural University, Beijing 100193, China|Department of Botany and Plant Sciences, Center for Plant Cell Biology, Institute of Integrative Genome Biology, University of California, Riverside, California 92521;
Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
College of Biological Science, China Agricultural University, Beijing 100193, China|China Agricultural University-University of California-Riverside Joint Center for Biological Sciences and Biotechnology, China Agricultural University, Beijing 100193, China;
Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
China Agricultural University-University of California-Riverside Joint Center for Biological Sciences and Biotechnology, China Agricultural University, Beijing 100193, China|Department of Botany and Plant Sciences, Center for Plant Cell Biology, Institute of Integrative Genome Biology, University of California, Riverside, California 92521;
