Iron (Fe) is an essential plant nutrient. Its deficiency is a major constraint in crop production systems, affecting crop yield and quality. It is therefore important to elucidate the responses and adaptive mechanisms underlying Fe-deficiency symptoms in alfalfa. The experiment was carried out on 12-day-old alfalfa plants grown in hydroponics under Fe-sufficient and Fe-deficient conditions. The Fe-starved alfalfa showed decreased plant biomass, chlorophyll score, PSII efficiency, and photosynthesis performance index in young leaves under low Fe. Further, Fe shortage reduced the Fe, Zn, S and Ca concentration in root and shoot of alfalfa accompanied by the marked decrease of MsIRT1, MsZIP, MsSULTR1;1, MsSULTR1;2 and MsSULTR1;3 transcripts in root and shoot. It indicates that retardation caused by Fe-deficiency was also associated with the status of other elements, especially the reduced Fe and S may be coordinately attributed to the photosynthetic damages in Fe-deficient alfalfa. The ferric chelate reductase activity accompanied by the expression of MsFRO1 in roots showed no substantial changes, indicating the possible involvement of this Strategy I response in Fe-deficient alfalfa. However, the proton extrusion and expression of MsHAI1 were significantly induced following Fe-deficiency. In silico analysis further suggested their subcellular localization in the plasma membrane. Also, the interactome map suggested the partnership of MsFRO1 with plasma membrane H+-ATPase, transcription factor bHLH47, and nitrate reductase genes, while MsHAI1 partners include ferric reductase-like transmembrane component, plasma membrane ATPase, vacuolar-type H-pyrophosphatase, and general regulatory factor 2. In this study, SOD and APX enzymes showed a substantial increase in roots but unable to restore the oxidative damages in Fe-starved alfalfa. These findings promote further studies for the improvement of Fe-starved alfalfa or legumes through breeding or transgenic approaches.

中文翻译：

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缺铁苜蓿的生长和生理损伤与铁和硫转运蛋白的下调以及氧化还原失衡有关

铁 (Fe) 是一种必需的植物营养素。它的缺乏是作物生产系统的主要制约因素，影响作物产量和质量。因此，阐明苜蓿缺铁症状的反应和适应机制非常重要。该实验是在铁充足和铁缺乏条件下在水培中生长的 12 天大的苜蓿植物上进行的。在低铁条件下，缺铁的苜蓿幼叶的植物生物量、叶绿素评分、PSII 效率和光合作用性能指数均降低。此外，铁缺乏降低了苜蓿根和芽中的 Fe、Zn、S 和 Ca 浓度，伴随着根和芽中 MsIRT1、MsZIP、MsSULTR1;1、MsSULTR1;2 和 MsSULTR1;3 转录本的显着减少。说明缺铁引起的发育迟缓也与其他元素的状态有关，尤其是铁和硫的减少可能与缺铁苜蓿的光合损伤协同作用。伴随根中 MsFRO1 表达的铁螯合还原酶活性没有显示出实质性变化，表明这种策略 I 反应可能涉及缺铁苜蓿。然而，在缺铁后，MsHAI1 的质子挤出和表达被显着诱导。计算机分析进一步表明它们在质膜中的亚细胞定位。此外，相互作用组图表明 MsFRO1 与质膜 H+-ATPase、转录因子 bHLH47 和硝酸还原酶基因的伙伴关系，而 MsHAI1 伙伴包括铁还原酶样跨膜成分、质膜 ATP 酶、液泡型 H-焦磷酸酶和一般调节因子 2。在本研究中，SOD 和 APX 酶在根中显示出显着增加但无法恢复氧化损伤缺铁的苜蓿。这些发现促进了通过育种或转基因方法改进缺铁苜蓿或豆类的进一步研究。