Figure 2.

A hypothetical model of rapid plasmodesmata aperture regulation. The auxin influx may induce calcium ion release in the upper tier cells. Next, a high calcium concentration in the cytoplasm triggers changes in the conformation of myosin and synaptotagmin proteins, which reduce the aperture of the neck region at one side of the plasmodesma. This could favor unidirectional auxin movement, which may underlie the establishment of different auxin maxima in adjacent cells. This mechanism could also induce a reduction of cell-to-cell communication if calcium release happens in both cells.