Varnum-Finney B J, Voss E, Soll D R
Department of Biology, University of Iowa, Iowa City 52242.
Cell Motil Cytoskeleton. 1987;8(1):18-26. doi: 10.1002/cm.970080104.
Amebae of Dictyostelium discoideum normally chemotax to aggregation centers by assessing the direction of outwardly moving, nondissipating waves of the chemoattractant cAMP. However, D. discoideum amebae can also assess the direction of a relatively stable spatial gradient. We demonstrate that amebae migrating towards the "source" of a stable, spatial gradient move faster, extend fewer pseudopodia, and turn less frequently than amebae migrating away from the "source" in the same spatial gradient. In addition, amebae extend lateral pseudopods in a polarized fashion from the anterior half of the cell, and do so as frequently towards the source as away from the source. However, those formed towards the source more often produce a turn than those formed away from the source. These results suggest that there may be two decision-making systems, one localized in the pseudopods, and one along the entire cell body; they support the suggestion that Dictyostelium amebae may employ a temporal mechanism to assess the direction of a spatial gradient of chemoattractant.
盘基网柄菌的变形虫通常通过评估趋化因子cAMP向外移动且不消散的波的方向，向聚集中心进行趋化运动。然而，盘基网柄菌变形虫也能够评估相对稳定的空间梯度的方向。我们证明，在相同空间梯度中，朝着稳定空间梯度的“源”迁移的变形虫比背离“源”迁移的变形虫移动速度更快、伸出的伪足更少且转向频率更低。此外，变形虫从细胞前半部分以极化方式伸出侧向伪足，朝着源伸出和背离源伸出的频率相同。然而，朝着源形成的伪足比背离源形成的伪足更常导致转向。这些结果表明可能存在两种决策系统，一种位于伪足中，另一种沿整个细胞体；它们支持盘基网柄菌变形虫可能采用一种时间机制来评估趋化因子空间梯度方向的观点。
