Department of Botany, Ecology and Plant Physiology, Edificio Celestino Mutis C-4, Campus de Rabanales, University of Córdoba, 14014 Córdoba, Spain.
Planta. 2013 Jan;237(1):65-75. doi: 10.1007/s00425-012-1757-0. Epub 2012 Sep 15.
Previous research showed that auxin, ethylene, and nitric oxide (NO) can activate the expression of iron (Fe)-acquisition genes in the roots of Strategy I plants grown with low levels of Fe, but not in plants grown with high levels of Fe. However, it is still an open question as to how Fe acts as an inhibitor and which pool of Fe (e.g., root, phloem, etc.) in the plant acts as the key regulator for gene expression control. To further clarify this, we studied the effect of the foliar application of Fe on the expression of Fe-acquisition genes in several Strategy I plants, including wild-type cultivars of Arabidopsis [Arabidopsis thaliana (L.) Heynh], pea [Pisum sativum L.], tomato [Solanum lycopersicon Mill.], and cucumber [Cucumis sativus L.], as well as mutants showing constitutive expression of Fe-acquisition genes when grown under Fe-sufficient conditions [Arabidopsis opt3-2 and frd3-3, pea dgl and brz, and tomato chln (chloronerva)]. The results showed that the foliar application of Fe blocked the expression of Fe-acquisition genes in the wild-type cultivars and in the frd3-3, brz, and chln mutants, but not in the opt3-2 and dgl mutants, probably affected in the transport of a Fe-related repressive signal in the phloem. Moreover, the addition of either ACC (ethylene precursor) or GSNO (NO donor) to Fe-deficient plants up-regulated the expression of Fe-acquisition genes, but this effect did not occur in Fe-deficient plants sprayed with foliar Fe, again suggesting the existence of a Fe-related repressive signal moving from leaves to roots.
先前的研究表明，生长素、乙烯和一氧化氮 (NO) 可以激活低铁水平下策略 I 植物根系中铁（Fe）获取基因的表达，但在高铁水平下则不会。然而，Fe 如何作为抑制剂起作用以及植物中哪个铁池（例如根、韧皮部等）作为基因表达控制的关键调节剂仍然是一个悬而未决的问题。为了进一步阐明这一点，我们研究了叶面喷施 Fe 对几种策略 I 植物中铁获取基因表达的影响，包括拟南芥 [Arabidopsis thaliana (L.) Heynh]、豌豆 [Pisum sativum L.]、番茄 [Solanum lycopersicon Mill.] 和黄瓜 [Cucumis sativus L.] 的野生型品种，以及在铁充足条件下表现出铁获取基因组成型表达的突变体 [Arabidopsis opt3-2 和 frd3-3、豌豆 dgl 和 brz 以及番茄 chln (chloronerva)]。结果表明，叶面喷施 Fe 阻断了野生型品种以及 frd3-3、brz 和 chln 突变体中铁获取基因的表达，但对 opt3-2 和 dgl 突变体则没有影响，可能是韧皮部中与 Fe 相关的抑制信号的运输受到了影响。此外，将 ACC（乙烯前体）或 GSNO（NO 供体）添加到缺铁植物中可以上调铁获取基因的表达，但在叶面喷施 Fe 的缺铁植物中则不会发生这种情况，这再次表明存在一种从叶片向根部传递的与 Fe 相关的抑制信号。
