Oparka K J, Roberts A G, Boevink P, Santa Cruz S, Roberts I, Pradel K S, Imlau A, Kotlizky G, Sauer N, Epel B
Unit of Cell Biology, Scottish Crop Research Institute, Invergowrie, Dundee, United Kingdom.
Cell. 1999 Jun 11;97(6):743-54. doi: 10.1016/s0092-8674(00)80786-2.
Leaves undergo a sink-source transition during which a physiological change occurs from carbon import to export. In sink leaves, biolistic bombardment of plasmids encoding GFP-fusion proteins demonstrated that proteins with an Mr up to 50 kDa could move freely through plasmodesmata. During the sink-source transition, the capacity to traffic proteins decreased substantially and was accompanied by a developmental switch from simple to branched forms of plasmodesmata. Inoculation of sink leaves with a movement protein-defective virus showed that virally expressed GFP, but not viral RNA, was capable of trafficking between sink cells during infection. Contrary to dogma that plasmodesmata have a size exclusion limit below 1 kDa, the data demonstrate that nonspecific "macromolecular trafficking" is a general feature of simple plasmodesmata in sink leaves.
叶片会经历从库到源的转变，在此过程中会发生从碳输入到输出的生理变化。在库叶片中，对编码绿色荧光蛋白（GFP）融合蛋白的质粒进行生物弹道轰击表明，分子量高达50 kDa的蛋白质能够通过胞间连丝自由移动。在从库到源的转变过程中，蛋白质运输能力大幅下降，并伴随着胞间连丝从简单形式向分支形式的发育转变。用一种缺乏运动蛋白的病毒接种库叶片表明，病毒表达的GFP能够在感染期间在库细胞之间运输，而病毒RNA则不能。与胞间连丝的大小排阻极限低于1 kDa的传统观念相反，这些数据表明非特异性的“大分子运输”是库叶片中简单胞间连丝的一个普遍特征。
