Microtubule-dependent targeting of the exocyst complex is necessary for xylem development in Arabidopsis.
Microtubule-dependent targeting of the exocyst complex is necessary for xylem development in Arabidopsis.
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DOI：
10.1111/nph.14267
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发表时间：
2017-02
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通讯作者：
Nemanja Vukašinović;Y. Oda;P. Pejchar;Lukáš Synek;T. Pečenková;Anamika A Rawat;Juraj Sekereš;M. Potocký;V. Žárský
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作者：
Nemanja Vukašinović;Y. Oda;P. Pejchar;Lukáš Synek;T. Pečenková;Anamika A Rawat;Juraj Sekereš;M. Potocký;V. Žárský
皮层微管（MT）通过决定次生细胞壁（SCW）沉积的位点，在管状分子（TE）中次生细胞壁（SCW）增厚的模式中起着重要作用。外囊分泌囊泡栓系复合物的EXO 70 A1亚基被认为是通过MT相互作用对TE发育的重要作用。我们研究了拟南芥木质部中几个外囊亚基的亚细胞定位，并分析了外囊介导的运输在TE发育中的功能意义。使用共聚焦显微镜和蛋白质-蛋白质相互作用测定法对TE中荧光标记的外囊亚基进行活细胞成像，以描述外囊及其伙伴在TE发展中的作用。在TEs中，外囊亚基以MT依赖的方式定位于SCW沉积的位点。我们提出，外囊靶向MT的机制涉及外囊亚基与COG 2蛋白的直接相互作用。我们证明了功能性外囊亚基EXO 84 b对于正常TE发育的重要性，并表明SCW成分的沉积部分受到损害，这可能是外囊突变体中二级纤维素合酶错误定位的结果。我们的结论是外囊复合物是一个重要的因素，桥接模式定义的皮质MT与本地化分泌的SCW在开发TE。
Cortical microtubules (MTs) play a major role in the patterning of secondary cell wall (SCW) thickenings in tracheary elements (TEs) by determining the sites of SCW deposition. The EXO70A1 subunit of the exocyst secretory vesicle tethering complex was implicated to be important for TE development via the MT interaction. We investigated the subcellular localization of several exocyst subunits in the xylem of Arabidopsis thaliana and analyzed the functional significance of exocyst-mediated trafficking in TE development. Live cell imaging of fluorescently tagged exocyst subunits in TE using confocal microscopy and protein-protein interaction assays were performed to describe the role of the exocyst and its partners in TE development. In TEs, exocyst subunits were localized to the sites of SCW deposition in an MT-dependent manner. We propose that the mechanism of exocyst targeting to MTs involves the direct interaction of exocyst subunits with the COG2 protein. We demonstrated the importance of a functional exocyst subunit EXO84b for normal TE development and showed that the deposition of SCW constituents is partially compromised, possibly as a result of the mislocalization of secondary cellulose synthase in exocyst mutants. We conclude that the exocyst complex is an important factor bridging the pattern defined by cortical MTs with localized secretion of the SCW in developing TEs.