Schmidt W, Tittel J, Schikora A
Carl von Ossietzky Universität Oldenburg, Fachbereich Biologie, 26111 Oldenburg, Postfach 2503, Germany.
Plant Physiol. 2000 Apr;122(4):1109-18. doi: 10.1104/pp.122.4.1109.
In "strategy I" plants, several alterations in root physiology and morphology are induced by Fe deficiency, although the mechanisms by which low Fe levels are translated into reactions aimed at alleviating Fe shortage are largely unknown. To prove whether changes in hormone concentration or sensitivity are involved in the adaptation to suboptimal Fe availability, we tested 45 mutants of Arabidopsis defective in hormone metabolism and/or root hair formation for their ability to increase Fe(III) chelate reductase activity and to initiate the formation and enlargement of root hairs. Activity staining for ferric chelate reductase revealed that all mutants were responsive to Fe deficiency, suggesting that hormones are not necessary for the induction. Treatment of wild-type plants with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid caused the development of root hairs in locations normally occupied by non-hair cells, but did not stimulate ferric reductase activity. Ectopic root hairs were also formed in -Fe roots, suggesting a role for ethylene in the morphological responses to Fe deficiency. Ultrastructural analysis of rhizodermal cells indicated that neither Fe deficiency nor 1-aminocyclopropane-1-carboxylic acid treatment caused transfer-cell-like alterations in Arabidopsis roots. Our data indicate that the morphological and physiological components of the Fe stress syndrome are regulated separately.
在“策略I”植物中，缺铁会诱导根系生理和形态发生多种变化，尽管低铁水平转化为旨在缓解铁短缺反应的机制在很大程度上尚不清楚。为了证明激素浓度或敏感性的变化是否参与了对次优铁有效性的适应，我们测试了45个拟南芥激素代谢和/或根毛形成缺陷的突变体，以评估它们提高铁（III）螯合物还原酶活性以及启动根毛形成和伸长的能力。铁螯合物还原酶的活性染色显示，所有突变体对缺铁都有反应，这表明激素对于诱导过程并非必需。用乙烯前体1-氨基环丙烷-1-羧酸处理野生型植物，会导致在通常由非根毛细胞占据的位置形成根毛，但不会刺激铁还原酶活性。在缺铁根中也形成了异位根毛，这表明乙烯在对缺铁的形态学反应中发挥作用。根表皮细胞的超微结构分析表明，缺铁和1-氨基环丙烷-1-羧酸处理均未在拟南芥根中引起类似传递细胞的变化。我们的数据表明，铁胁迫综合征的形态学和生理学成分是分别调控的。
