Rashotte A M, Brady S R, Reed R C, Ante S J, Muday G K
Department of Biology, Wake Forest University, Box 7325, Winston-Salem, North Carolina 27109-7325, USA.
Plant Physiol. 2000 Feb;122(2):481-90. doi: 10.1104/pp.122.2.481.
Auxin transport has been reported to occur in two distinct polarities, acropetally and basipetally, in two different root tissues. The goals of this study were to determine whether both polarities of indole-3-acetic acid (IAA) transport occur in roots of Arabidopsis and to determine which polarity controls the gravity response. Global application of the auxin transport inhibitor naphthylphthalamic acid (NPA) to roots blocked the gravity response, root waving, and root elongation. Immediately after the application of NPA, the root gravity response was completely blocked, as measured by an automated video digitizer. Basipetal [(3)H]IAA transport in Arabidopsis roots was inhibited by NPA, whereas the movement of [(14)C]benzoic acid was not affected. Inhibition of basipetal IAA transport by local application of NPA blocked the gravity response. Inhibition of acropetal IAA transport by application of NPA at the root-shoot junction only partially reduced the gravity response at high NPA concentrations. Excised root tips, which do not receive auxin from the shoot, exhibited a normal response to gravity. The Arabidopsis mutant eir1, which has agravitropic roots, exhibited reduced basipetal IAA transport but wild-type levels of acropetal IAA transport. These results support the hypothesis that basipetally transported IAA controls root gravitropism in Arabidopsis.
据报道，生长素运输在两种不同的根组织中以两种不同的极性发生，即向顶运输和向基运输。本研究的目的是确定吲哚 - 3 - 乙酸（IAA）运输的两种极性是否都在拟南芥根中发生，并确定哪种极性控制重力反应。将生长素运输抑制剂萘基邻苯二甲酸（NPA）全局应用于根会阻断重力反应、根摆动和根伸长。在应用NPA后立即通过自动视频数字化仪测量，根重力反应被完全阻断。拟南芥根中的向基[（3）H]IAA运输受到NPA抑制，而[（14）C]苯甲酸的移动不受影响。通过局部应用NPA抑制向基IAA运输会阻断重力反应。仅在根 - 茎连接处应用NPA抑制向顶IAA运输，在高NPA浓度下仅部分降低重力反应。未从地上部接收生长素的离体根尖对重力表现出正常反应。具有无向重力性根的拟南芥突变体eir1表现出向基IAA运输减少，但向顶IAA运输水平与野生型相同。这些结果支持这样的假设，即向基运输的IAA控制拟南芥根的向重力性。
