Long-distance signals positively regulate the expression of iron uptake genes in tobacco roots
Long-distance signals positively regulate the expression of iron uptake genes in tobacco roots
复制标题
DOI：
10.1007/s00425-007-0596-x
复制
发表时间：
2007-12-01
期刊：
影响因子：
4.3
通讯作者：
Goto, Fumiyuki
中科院分区：
文献类型：
--
作者：
Enomoto, Yusuke;Hodoshima, Hirotaka;Goto, Fumiyuki
地上部产生的长距离信号被认为与根对铁吸收的调节有关，然而，信号机制仍不清楚。为了阐明信号是正向还是负向调控根中的铁吸收基因，我们分析了两个具有代表性的铁吸收基因NtIRT1和NtFRO在烟草中的表达。根，经过试管处理后的根。缺铁叶片经Fe(II)-EDTA处理后，这两个基因的表达均显著降低，但根中的铁浓度与缺铁条件下生长的根中的铁浓度基本持平。接下来，在缺铁条件下生长的烟草植株的所有烟叶都被切除。两个基因的表达在叶片切除后2小时内迅速降低到一半以下，并在24小时后逐渐消失。比较了不同剪叶方式的植株中NtIRT1的表达。该基因的表达与缺铁叶片的干重成正比，但与切叶的位置无关。有趣的是，NtIRT1在缺铁条件下在毛状根中的表达增加，这表明根和地上部一样也具有铁状态的信号机制。综上所述，这些结果表明，在包括根在内的缺铁组织中产生的长距离信号是正向调控NtIRT1和NtFRO1在根中表达的主要因素，并且信号的强度取决于植物的大小。
Long-distance signals generated in shoots are thought to be associated with the regulation of iron uptake from roots; however, the signaling mechanism is still unknown. To elucidate whether the signal regulates iron uptake genes in roots positively or negatively, we analyzed the expressions of two representative iron uptake genes: NtIRT1 and NtFRO] in tobacco (Nicotiana tabacum L.) roots, after shoots were manipulated in vitro. When iron-deficient leaves were treated with Fe(II)-EDTA, the expressions of both genes were significantly reduced; nevertheless iron concentration in the roots maintained a similar level to that in roots grown under iron-deficient conditions. Next, all leaves from tobacco plants grown under the iron-deficient condition were excised. The expression of two genes were quickly reduced below half within 2 h after the leaf excision and gradually disappeared by the end of a 24-h period. The NtIRT1 expression was compared among the plants whose leaves were cut off in various patterns. The expression increased in proportion to the dry weight of iron-deficient leaves, although no relation was observed between the gene expression and the position of excised leaves. Interestingly, the NtIRT1 expression in hairy roots increased under the iron-deficient condition, suggesting that roots also have the signaling mechanism of iron status as well as shoots. Taken together, these results indicate that the long-distance signal generated in iron-deficient tissues including roots is a major factor in positive regulation of the expression of NtIRT1 and NtFRO1 in roots, and that the strength of the signal depends on the size of plants.