Directionality of Plasmodesmata-Mediated Transport in Arabidopsis Leaves Supports Auxin Channeling
Directionality of Plasmodesmata-Mediated Transport in Arabidopsis Leaves Supports Auxin Channeling
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DOI：
10.1016/j.cub.2020.03.014
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发表时间：
2020-05-18
期刊：
影响因子：
9.2
通讯作者：
Liesche, Johannes
中科院分区：
文献类型：
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作者：
Gao, Chen;Liu, Xiangdong;Liesche, Johannes
植物激素生长素是生长和发育的主要调节因子。质膜中的生长素转运蛋白被认为定义了生长素分布的组织水平模式[1，2]。然而，生长素足够小，可以通过连接相邻细胞的胞间连丝扩散[3]，提供了一种替代途径，其对生长素运输的贡献在很大程度上尚未探索[4]。在这里，光活化显微镜[5，6]用于测量拟南芥叶表皮中小分子扩散的能力。在覆盖中脉和叶柄的细长表皮细胞中，胞间连丝介导的细胞壁渗透性被发现在纵向上比在横向上高几倍。这种不对称性的生理相关性通过量化避荫反应进行了测试，避荫反应取决于生长素从叶尖到叶远轴侧叶柄的运输[7]，假设扩散的方向性补充了转运蛋白介导的生长素运动[8]。通过在顶端施用生长素来触发响应，导致野生型植物的叶片运动比缺乏建立方向性所必需的胼胝质合酶的gsl8突变体更强[9]。结果符合生长素运输的数学模型的预测的基础上测得的野生型和突变体植物的渗透性。它的结论是，胞间连丝的渗透性可以选择性地调制在植物细胞内，所赋予的方向性扩散可以影响小分子，如生长素的组织特异性分布模式。
The plant hormone auxin serves as central regulator of growth and development. Auxin transporters in the plasma membrane are assumed to define tissue-level patterns of auxin distribution [1, 2]. However, auxin is small enough to diffuse through the plasmodesmata that connect neighboring cells [3], presenting an alternative pathway, whose contribution to auxin transport remained largely unexplored [4]. Here, photoactivation microscopy [5, 6] was used to measure the capacity for small-molecule diffusion in the epidermis of Arabidopsis thaliana leaves. In the elongated epidermis cells covering the midrib and petiole, the plasmodesmata-mediated cell-wall permeability was found to be several times higher in the longitudinal than in the transverse direction. The physiological relevance of this asymmetry was tested through quantification of the shade-avoidance response, which depends on auxin transport from the leaf tip to the petiole in the abaxial side of the leaf [7], with the hypothesis that directionality of diffusion supplements transporter-mediated auxin movement [8]. Triggering the response by auxin application at the tip led to stronger leaf movement in wild-type plants than in gsl8 mutants [9], which lack the callose synthase necessary to establish directionality. The results match the predictions of a mathematical model of auxin transport based on the permeabilities measured in wild-type and mutant plants. It is concluded that plasmodesmata permeability can be selectively modulated within a plant cell and that the conferred directionality in diffusion can influence the tissue-specific distribution patterns of small molecules, like auxin.