Magnesium supply alleviates iron toxicity-induced leaf bronzing in rice through exclusion and tissue-tolerance mechanisms.
Magnesium supply alleviates iron toxicity-induced leaf bronzing in rice through exclusion and tissue-tolerance mechanisms.
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DOI：
10.3389/fpls.2023.1213456
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发表时间：
2023
影响因子：
5.6
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中科院分区：
文献类型：
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铁 (Fe) 毒性是低地水稻中普遍存在的营养失调，会导致生长迟缓和叶片症状（称为叶片古铜色）。部分原因是铁以外的营养物质不平衡造成的，已知供应这些物质可以减轻毒性。但所涉及的生理和分子机制尚不清楚。我们在马达加斯加中部高地的实地研究和过量铁（300 mg Fe L-1）的水培实验中研究了镁 (Mg) 对铁毒性耐受性的影响。在水培实验中进行了 RNA-seq 分析，以阐明镁效应的可能机制。在田间和水培条件下，添加镁始终会降低叶子的青铜色，而添加钾 (K) 则造成轻微影响。用镁处理的植物在田间往往具有较小的芽铁浓度，这表明在整个植物水平上增强了排除。然而，对多种基因型的分析表明，铁毒性症状也得到减轻，而铁浓度并未随之降低，这表明镁供应的增加赋予了组织水平的耐受性。水培实验还表明，镁减轻了叶子的青铜色，但没有显着降低铁浓度或氧化应激（根据氧化应激生物标志物丙二醛的含量评估）。 RNA-seq 分析表明，镁诱导的叶子变化多于根部变化。随后的顺式元件分析表明，NAC转录因子结合位点在叶子中铁毒性诱导的基因中富集。添加 Mg 导致相同结合位点的非显着富集，表明 NAC 家族蛋白可能介导 Mg 的作用。这项研究为减轻铁毒性引起的水稻叶片古铜色提供了线索。
Iron (Fe) toxicity is a widespread nutritional disorder in lowland rice causing growth retardation and leaf symptoms referred to as leaf bronzing. It is partly caused by an imbalance of nutrients other than Fe and supply of these is known to mitigate the toxicity. But the physiological and molecular mechanisms involved are unknown. We investigated the effect of magnesium (Mg) on Fe toxicity tolerance in a field study in the Central Highlands of Madagascar and in hydroponic experiments with excess Fe (300 mg Fe L-1). An RNA-seq analysis was conducted in a hydroponic experiment to elucidate possible mechanisms underlying Mg effects. Addition of Mg consistently decreased leaf bronzing under both field and hydroponic conditions, whereas potassium (K) addition caused minor effects. Plants treated with Mg tended to have smaller shoot Fe concentrations in the field, suggesting enhanced exclusion at the whole-plant level. However, analysis of multiple genotypes showed that Fe toxicity symptoms were also mitigated without a concomitant decrease of Fe concentration, suggesting that increased Mg supply confers tolerance at the tissue level. The hydroponic experiments also suggested that Mg mitigated leaf bronzing without significantly decreasing Fe concentration or oxidative stress as assessed by the content of malondialdehyde, a biomarker for oxidative stress. An RNA-seq analysis revealed that Mg induced more changes in leaves than roots. Subsequent cis-element analysis suggested that NAC transcription factor binding sites were enriched in genes induced by Fe toxicity in leaves. Addition of Mg caused non-significant enrichment of the same binding sites, suggesting that NAC family proteins may mediate the effect of Mg. This study provides clues for mitigating Fe toxicity-induced leaf bronzing in rice.