Graziano Magdalena, Lamattina Lorenzo
Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CC 1245, 7600 Mar del Plata, Argentina.
Plant J. 2007 Dec;52(5):949-60. doi: 10.1111/j.1365-313X.2007.03283.x. Epub 2007 Sep 22.
Iron is an essential and commonly limited nutrient for plants. To increase the uptake of iron during times of low iron supply, plants, except the grasses, activate a set of physiological and morphological responses in their roots that include iron reduction, soil acidification, Fe(II) transport and proliferation of root hairs. It is not known how root cells sense and transduce the changes that occur after the onset of iron deficiency. This work presents evidence that nitric oxide (NO) is produced rapidly in the root epidermis of tomato plants (Solanum lycopersicum) that are grown in iron-deficient conditions. The scavenging of NO prevented iron-deficiency-induced upregulation of the basic helix-loop-helix transcription factor FER, the ferric-chelate reductase LeFRO1 and the Fe(II) transporter LeIRT1 genes. On the other hand, exogenous application of the NO donor S-nitrosoglutathione enhanced the accumulation of FER, LeFRO1 and LeIRT1 mRNA in roots of iron-deficient plants. The activity of the root ferric-chelate reductase and the proliferation of root hairs induced by iron deficiency were stimulated by NO supplementation and suppressed by NO scavenging. Nitric oxide was ineffective in inducing iron-deficiency responses in the tomato fer mutant, which indicates that the FER protein is necessary to mediate the action of NO. Furthermore, NO supplementation improved plant growth under low iron supply, which suggests that NO is a key component of the regulatory mechanisms that control iron uptake and homeostasis in plants. In summary, the results of this investigation indicate that an increase in NO production is an early response of roots to iron deprivation that contributes to the improvement of iron availability by (i) modulating the expression of iron uptake-related genes and (ii) regulating the physiological and morphological adaptive responses of roots to iron-deficient conditions.
铁是植物必需但通常会受限的养分。为了在铁供应不足时增加铁的吸收，除禾本科植物外，植物会在根部激活一系列生理和形态反应，包括铁还原、土壤酸化、Fe(II)转运以及根毛增殖。目前尚不清楚根细胞如何感知并传导缺铁开始后发生的变化。这项研究提供了证据，表明在缺铁条件下生长的番茄植株（番茄）根表皮中会迅速产生一氧化氮（NO）。清除NO可阻止缺铁诱导的碱性螺旋-环-螺旋转录因子FER、铁螯合物还原酶LeFRO1和Fe(II)转运蛋白LeIRT1基因的上调。另一方面，外源施加NO供体S-亚硝基谷胱甘肽可增强缺铁植物根中FER、LeFRO1和LeIRT1 mRNA的积累。缺铁诱导的根铁螯合物还原酶活性和根毛增殖受到NO补充的刺激，并被NO清除所抑制。一氧化氮在番茄fer突变体中诱导缺铁反应无效，这表明FER蛋白是介导NO作用所必需的。此外，补充NO可改善低铁供应条件下的植物生长，这表明NO是控制植物铁吸收和体内平衡的调控机制的关键组成部分。总之，这项研究结果表明，NO生成增加是根对铁缺乏的早期反应，通过（i）调节铁吸收相关基因的表达和（ii）调节根对缺铁条件的生理和形态适应性反应，有助于提高铁的有效性。
