Aung May Sann, Masuda Hiroshi
Department of Biological Production, Faculty of Bioresource Sciences, Akita Prefectural University, Akita, Japan.
Front Plant Sci. 2020 Aug 7;11:1102. doi: 10.3389/fpls.2020.01102. eCollection 2020.
Iron (Fe) is an essential nutrient for all living organisms but can lead to cytotoxicity when present in excess. Fe toxicity often occurs in rice grown in submerged paddy fields with low pH, leading dramatical increases in ferrous ion concentration, disrupting cell homeostasis and impairing growth and yield. However, the underlying molecular mechanisms of Fe toxicity response and tolerance in plants are not well characterized yet. Microarray and genome-wide association analyses have shown that rice employs four defense systems to regulate Fe homeostasis under Fe excess. In defense 1, Fe excess tolerance is implemented by Fe exclusion as a result of suppression of genes involved in Fe uptake and translocation such as , , , , , , , , , and . The Fe-binding ubiquitin ligase, HRZ, is a key regulator that represses Fe uptake genes in response to Fe excess in rice. In defense 2, rice retains Fe in the root system rather than transporting it to shoots. In defense 3, rice compartmentalizes Fe in the shoot. In defense 2 and 3, the vacuolar Fe transporter , Fe storage protein ferritin, and the nicotinamine synthase mediate the isolation or detoxification of excess Fe. In defense 4, rice detoxifies the ROS produced within the plant body in response to excess Fe. Some transcription factors, variants, p450-family proteins, and , , and are implicated in defense 4. These knowledge will facilitate the breeding of tolerant crops with increased productivity in low-pH, Fe-excess soils.
铁（Fe）是所有生物必需的营养元素，但过量时会导致细胞毒性。铁毒性常在低pH值的淹水稻田中种植的水稻中发生，导致亚铁离子浓度急剧增加，破坏细胞内稳态并损害生长和产量。然而，植物中铁毒性反应和耐受性的潜在分子机制尚未得到很好的表征。微阵列和全基因组关联分析表明，水稻在铁过量时采用四种防御系统来调节铁稳态。在防御1中，由于抑制参与铁吸收和转运的基因（如 、 、 、 、 、 、 、 、 、 和 ），通过铁排斥实现铁过量耐受性。铁结合泛素连接酶HRZ是水稻中响应铁过量抑制铁吸收基因的关键调节因子。在防御2中，水稻将铁保留在根系中而不是运输到地上部分。在防御3中，水稻将铁在地上部分进行区室化。在防御2和3中，液泡铁转运蛋白 、铁储存蛋白铁蛋白和烟酰胺合酶介导过量铁的隔离或解毒。在防御4中，水稻对因铁过量在植物体内产生的活性氧进行解毒。一些 转录因子、 变体、p450家族蛋白以及 、 和 参与防御4。这些知识将有助于培育在低pH值、铁过量土壤中具有更高生产力的耐性作物。
