Natural Auxin Does Not Inhibit Brefeldin A Induced PIN1 and PIN2 Internalization in Root Cells
Natural Auxin Does Not Inhibit Brefeldin A Induced PIN1 and PIN2 Internalization in Root Cells
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DOI：
10.3389/fpls.2019.00574
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发表时间：
2019-05-09
影响因子：
5.6
通讯作者：
Palme, Klaus
中科院分区：
文献类型：
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作者：
Paponov, Ivan A.;Friz, Tatyana;Palme, Klaus
囊泡运输抑制剂Brefeldin A（BFA）通过诱导它们在细胞内的积累来改变质膜定位的PIN（作为极性生长素流出载体的蛋白质）的定位。用合成的生长素1-NAA预处理减少了BFA诱导的PIN内化，表明生长素化合物抑制PIN蛋白的内吞作用。然而，最重要的天然生长素，IAA，并没有实质性地抑制PIN内化，除非补充抗氧化剂，丁基羟基甲苯（BHT），也包括在孵育培养基中。我们问是否可以解释由IAA单独引起的相对较小的抑制作用，其在孵育溶液中的不稳定性或IAA是否可能与BHT相互作用，以抑制内吞作用。对培养液中IAA浓度和根中DR 5报告活性的分析表明，IAA在培养基中既稳定又有活性。因此，IAA降解不能解释IAA不能抑制内吞作用。此外，当在不存在生长素的情况下施用时，BHT引起PIN 1内化速率的强烈增加和PIN 2内化速率的较弱增加。这些增加不受IAA的同时应用，进一步表明，内吞作用是不受抑制的天然生长素IAA在生理相关的条件下。内吞作用被抑制在相同的速率与2-NAA，一种无活性的生长素类似物，观察到与1-NAA和更强烈的比天然生长素，支持的想法，这种抑制不是生长素特异性的。
The vesicle trafficking inhibitor Brefeldin A (BFA) changes the localization of plasma membrane localized PINs, proteins that function as polar auxin efflux carriers, by inducing their accumulation within cells. Pretreatment with the synthetic auxin 1-NAA reduces this BFA-induced PIN internalization, suggesting that auxinic compounds inhibit the endocytosis of PIN proteins. However, the most important natural auxin, IAA, did not substantially inhibit PIN internalization unless a supplementary antioxidant, butylated hydroxytoluene (BHT), was also included in the incubation medium. We asked whether the relatively small inhibition caused by IAA alone could be explained by its instability in the incubation solution or whether IAA might interact with BHT to inhibit endocytosis. Analysis of the IAA concentration in the incubation solution and of DR5 reporter activity in the roots showed that IAA is both stable and active in the medium. Therefore, IAA degradation was not able to explain the inability of IAA to inhibit endocytosis. Furthermore, when applied in the absence of auxin, BHT caused a strong increase in the rate of PIN1 internalization and a weaker increase in the rate of PIN2 internalization. These increases were unaffected by the simultaneous application of IAA, further indicating that endocytosis is not inhibited by the natural auxin IAA under physiologically relevant conditions. Endocytosis was inhibited at the same rate with 2-NAA, an inactive auxin analog, as was observed with 1-NAA and more strongly than with natural auxins, supporting the idea that this inhibition is not auxin specific.