Evidence for Unidirectional Flow through Plasmodesmata
Evidence for Unidirectional Flow through Plasmodesmata
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DOI：
10.1104/pp.109.137083
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发表时间：
2009-05-01
期刊：
影响因子：
7.4
通讯作者：
Oparka, Karl
中科院分区：
文献类型：
--
作者：
Christensen, Nynne Meyn;Faulkner, Christine;Oparka, Karl
烟草（Nicotiana tabacum）叶毛是一种独特的分泌结构，其基部毛细胞通过大量的胞间连丝（PD）与表皮相连。小的荧光探针显微注射到基部毛细胞移动顶端到远端毛细胞，但不对着表皮细胞。与此形成鲜明对比的是，当将相同的探针注射到表皮细胞中时，探针向顶端移动进入毛状体细胞。非侵入性方法的染料加载，包括酯加载到顶端分泌细胞的毛状体“盖帽”和笼状荧光素的渗透，产生了相同的结果。在组成型表达光活化绿色荧光蛋白（PAGFP）的转基因烟草植株中，在表皮/毛状体（e/t）边界上方激活的PAGFP导致蛋白质向顶端移动进入远端毛状体细胞，但不穿过e/t边界，而在表皮细胞中激活的PAGFP向顶端移动穿过e/t边界。质外体示踪剂的实验也揭示了一个独特的质外体障碍溶质运动在E/T界面的存在。这些数据表明溶质通过PD单向转运。PAGFP激活的单个细胞之间的等距的基底细胞和顶端细胞从这些细胞双向移动，这表明质量流不是单向运输的驱动力。我们发现，单向运输跨越E/T边界不受病毒感染或通过添加肌动蛋白抑制剂latrunculin，但可以完全消散通过添加叠氮化钠。总的来说，我们的数据表明，积极的，单向运输的分子可能会发生通过PD位于独特的接口在植物中。
The leaf trichome of tobacco (Nicotiana tabacum) represents a unique secretory structure in which the basal trichome cell is connected to the epidermis by numerous plasmodesmata (PD). Small fluorescent probes microinjected into the basal trichome cell moved apically into distal trichome cells but not into the subtending epidermal cell. In marked contrast, the same probes moved apically into trichome cells when injected into the epidermal cell. Noninvasive methods of dye loading, including ester loading into the apical secretory cell by trichome "capping" and by infiltration of caged fluorescein, produced the same result. In transgenic tobacco plants constitutively expressing photoactivatable green fluorescent protein (PAGFP), activation of PAGFP above the epidermal/trichome (e/t) boundary resulted in movement of protein apically into the distal trichome cells but not across the e/t boundary, while PAGFP activated in the epidermal cell moved apically across the e/t boundary. Experiments with apoplastic tracers also revealed the presence of a distinct apoplastic barrier to solute movement at the e/t interface. These data point to unidirectional transport of solutes through PD. PAGFP activated in individual cells equidistant between the basal cell and the apical cell moved bidirectionally from these cells, suggesting that mass flow was not the driving force for unidirectional transport. We found that unidirectional transport across the e/t boundary was not affected by virus infection or by addition of the actin inhibitor latrunculin but could be dissipated completely by addition of sodium azide. Collectively, our data suggest that active, unidirectional transport of molecules may occur through PD located at unique interfaces in the plant.