高铵胁迫对拟南芥幼苗侧根生长的影响及机制探索

Response and Mechanism of Arabidopsis Lateral Root to Excessive Ammonium Stress

本研究探讨了高铵对拟南芥幼苗侧根的影响特征及相关机制。结果表明,根部高铵明显地抑制拟南芥侧根生长,主要是降低侧根长度而非减少侧根数量。外源铵代谢抑制剂MSO不能缓解这种抑制效应,说明该效应可能并非N代谢产生的整体效应。对主根或侧根的不同区段进行局部供铵处理,发现根部高铵抑制侧根长是通过侧根根尖特异性介导的一种局部的直接抑制效应。同时,局部高铵对异侧非高铵区的二级侧根长度有显著的促进作用。突变体分析表明,生长素运输突变体aux1-7和eir1-1以及乙烯不敏感突变体ein2-1和etr1-3的侧根生长对高铵抑制效应均没有抗性,说明根部高铵抑制侧根生长的效应可能不是通过影响生长素运输和乙烯调控途径起作用的。

In this study, we investigated the responses and the mechanisms of the lateral root to root-supplied ammonium in Arabidopsis thaliana seedlings. The results indicated that high concentration of ammonium suppressed the lateral root development through the length of the lateral root rather than the number. Adding MSO showed no rescue of the lateral root length, suggesting that this inhibitory effect was not a systemic effect by the metabolism of excessive ammonium from root but a localized effect. The root tip of the lateral root was the cruciat perceived site, which was confirmed by the experiments of supplying ammonium to the different zones of primary or lateral root in Col-0. On the other hand, when ammonium was localized supplied to part of the root, the length of the lateral root on the other agar surface which did not contain ammonium was significantly promoted. According to the analyses of the relative mutants, the lateral root length of mutants both in auxin transport （auxl-7, eirl-1） and insensitive to ethylene （ein2-1, etrl-3） had no tolerance to this repressive effect of root-supplied ammonium on the relative length of the lateral root in Arabidopsis seedlings, which indicated that this effect may be mainly regulated by independent auxin-transport and ethylene pathways.