The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium
The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium
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DOI：
10.1105/tpc.15.01057
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发表时间：
2016-05-01
期刊：
影响因子：
11.6
通讯作者：
Hardtke, Christian S.
中科院分区：
文献类型：
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作者：
Pacheco-Villalobos, David;Diaz-Moreno, Sara M.;Hardtke, Christian S.
植物细胞伸长的长期酸性生长理论认为，生长素通过刺激细胞壁酸化从而促进细胞伸长。到目前为止，缺乏相关的遗传材料已经排除了彻底分析的重要性，这一概念的根源。最近分离的突变体的模式草种二穗短柄草与显着增强根细胞伸长，由于细胞生长素水平的增加，使我们能够解决这个问题。我们发现，主要的转录组学效应与伸长的根细胞中生长素浓度升高的稳态是上调细胞壁重塑因子，特别是expansins，而植物激素信号通路保持显着的稳态。这些变化特别伴随着细胞壁阿拉伯半乳聚糖复杂性降低，但不增加质子排泄。相反，我们观察到一种趋势，减少而不是增加质子从根伸长区细胞生长素水平较高。此外，类似于短柄草属，根细胞伸长，一般来说，在拟南芥中，对外部pH值波动的鲁棒缓冲。然而，通过人工质子泵激活的强制酸化抑制根细胞伸长。因此，生长素、质子泵激活和膨胀素作用之间的相互作用可能在根中比在芽中更灵活。
The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots.