Feng Haizhong, An Fengying, Zhang Suzhi, Ji Zhendong, Ling Hong-Qing, Zuo Jianru
State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China, 100101.
Plant Physiol. 2006 Apr;140(4):1345-54. doi: 10.1104/pp.105.074138. Epub 2006 Feb 17.
Iron is an essential element for almost all living organisms, actively involved in a variety of cellular activities. To acquire iron from soil, strategy I plants such as Arabidopsis (Arabidopsis thaliana) must first reduce ferric to ferrous iron by Fe(III)-chelate reductases (FROs). FRO genes display distinctive expression patterns in several plant species. However, regulation of FRO genes is not well understood. Here, we report a systematic characterization of the AtFRO6 expression during plant growth and development. AtFRO6, encoding a putative FRO, is specifically expressed in green-aerial tissues in a light-dependent manner. Analysis of mutant promoter-beta-glucuronidase reporter genes in transgenic Arabidopsis plants revealed the presence of multiple light-responsive elements in the AtFRO6 promoter. These light-responsive elements may act synergistically to confer light responsiveness to the AtFRO6 promoter. Moreover, no AtFRO6 expression was detected in dedifferentiated green calli of the korrigan1-2 (kor1-2) mutant or undifferentiated calli derived from wild-type explants. Conversely, AtFRO6 is expressed in redifferentiated kor1-2 shoot-like structures and differentiating calli of wild-type explants. In addition, AtFRO7, but not AtFRO5 and AtFRO8, also shows a reduced expression level in kor1-2 green calli. These results suggest that whereas photosynthesis is necessary but not sufficient, both light and cell differentiation are necessary for AtFRO6 expression. We propose that AtFRO6 expression is light regulated in a tissue- or cell differentiation-specific manner to facilitate the acquisition of iron in response to distinctive developmental cues.
铁是几乎所有生物的必需元素，积极参与各种细胞活动。为了从土壤中获取铁，拟南芥等I型植物必须首先通过铁（III）螯合物还原酶（FROs）将三价铁还原为二价铁。FRO基因在几种植物物种中表现出独特的表达模式。然而，FRO基因的调控尚不清楚。在这里，我们报告了AtFRO6在植物生长发育过程中的系统表征。AtFRO6编码一种假定的FRO，以光依赖的方式在绿色地上组织中特异性表达。对转基因拟南芥植物中突变体启动子 - β - 葡萄糖醛酸酶报告基因的分析揭示了AtFRO6启动子中存在多个光响应元件。这些光响应元件可能协同作用，赋予AtFRO6启动子光响应性。此外，在korrigan1 - 2（kor1 - 2）突变体的去分化绿色愈伤组织或野生型外植体来源的未分化愈伤组织中未检测到AtFRO6表达。相反，AtFRO6在kor1 - 2再分化的芽状结构和野生型外植体的分化愈伤组织中表达。此外，AtFRO7而非AtFRO5和AtFRO8在kor1 - 2绿色愈伤组织中的表达水平也降低。这些结果表明，虽然光合作用是必要的但不充分，光和细胞分化对于AtFRO6表达都是必要的。我们提出，AtFRO6的表达以组织或细胞分化特异性的方式受到光调控，以促进在独特发育线索响应中获取铁。
