Contrasting dynamics of radial O2-loss barrier induction and aerenchyma formation in rice roots of two lengths.
Contrasting dynamics of radial O2-loss barrier induction and aerenchyma formation in rice roots of two lengths.
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DOI：
10.1093/aob/mcq221
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发表时间：
2011
期刊：
影响因子：
4.2
通讯作者：
K. Shiono;Satoshi Ogawa;So Yamazaki;H. Isoda;T. Fujimura;M. Nakazono;T. Colmer
中科院分区：
文献类型：
--
作者：
K. Shiono;Satoshi Ogawa;So Yamazaki;H. Isoda;T. Fujimura;M. Nakazono;T. Colmer
背景和目的 许多湿地物种在根部形成通气组织和径向 O(2) 损失 (ROL) 的屏障。这些特征增强了内部 O(2) 向根尖的扩散。水稻中的屏障形成是由静止溶液中的生长诱导的，但缺乏对屏障诱导动力学和早期解剖学变化的了解。方法使用圆柱形根套O(2) 电极和用于O(2) 泄漏的亚甲基蓝指示剂染料来评估水稻短根和长根(Oryza sativa L.'Nipponbare') 的ROL 屏障感应。还在根横截面中监测通气组织的形成。通过透射电子显微镜（TEM）观察皮下/外皮层的微观结构。主要结果 在停滞培养基中，长不定根在数小时内开始形成 ROL 形成障碍，并在 24 小时内形成良好的障碍。相比之下，短根中屏障的形成需要超过 48 小时。短根和长根中通气组织形成增强的时间相同。 ROL 数据和随后的亚甲基蓝染色的比较确定了染料方法的表观 ROL 阈值，并且染料方法证实长根的屏障诱导比短根更快。屏障的形成可能与外皮周边细胞壁中新电子致密材料的沉积有关。组织化学染色表明木栓质沉积在木质素增加之前增强。结论 由于根长影响 ROL 屏障的形成，但不影响通气组织，因此这两种适应在水稻根部受到不同的调节。此外，ROL屏障诱导发生在可以看到假定的木栓质和木质素沉积物的组织化学可检测变化之前，而TEM显示外皮细胞壁中新的电子致密材料的沉积，因此屏障功能所需的结构变化似乎比之前描述的更微妙。
BACKGROUND AND AIMS Many wetland species form aerenchyma and a barrier to radial O(2) loss (ROL) in roots. These features enhance internal O(2) diffusion to the root apex. Barrier formation in rice is induced by growth in stagnant solution, but knowledge of the dynamics of barrier induction and early anatomical changes was lacking. METHODS ROL barrier induction in short and long roots of rice (Oryza sativa L. 'Nipponbare') was assessed using cylindrical root-sleeving O(2) electrodes and methylene blue indicator dye for O(2) leakage. Aerenchyma formation was also monitored in root cross-sections. Microstructure of hypodermal/exodermal layers was observed by transmission electron microscopy (TEM). KEY RESULTS In stagnant medium, barrier to ROL formation commenced in long adventitious roots within a few hours and the barrier was well formed within 24 h. By contrast, barrier formation took longer than 48 h in short roots. The timing of enhancement of aerenchyma formation was the same in short and long roots. Comparison of ROL data and subsequent methylene blue staining determined the apparent ROL threshold for the dye method, and the dye method confirmed that barrier induction was faster for long roots than for short roots. Barrier formation might be related to deposition of new electron-dense materials in the cell walls at the peripheral side of the exodermis. Histochemical staining indicated suberin depositions were enhanced prior to increases in lignin. CONCLUSIONS As root length affected formation of the barrier to ROL, but not aerenchyma, these two acclimations are differentially regulated in roots of rice. Moreover, ROL barrier induction occurred before histochemically detectable changes in putative suberin and lignin deposits could be seen, whereas TEM showed deposition of new electron-dense materials in exodermal cell walls, so structural changes required for barrier functioning appear to be more subtle than previously described.