Rice is one of the most susceptible plants to iron (Fe) deficiency under neutral and alkaline conditions. Alkaline stress induces H2 O2 production and increases the deposition of Fe on the root surface, which causes leaf chlorosis and Fe deficiency in rice. Gene chip and qRT-PCR analysis indicated that the expression of the nitrate reductase (NR) genes were downregulated by alkaline treatment, which resulted in significantly decreased nitrate activity and nitric oxide (NO) production in the epidermis and stele, where H2 O2 accumulated. In contrast, treatment with sodium nitroprusside (SNP), a NO donor, strongly alleviated alkaline-induced Fe deficiency by limiting Fe plaque formation. Increasing the NO signal significantly reduced the accumulation of H2 O2 and the lignin barrier but enhanced phenolic acid secretion in the root epidermis and stele under alkaline conditions. The secreted phenolic acid effectively mobilized the apoplast Fe and increased Fe uptake in roots, thereby alleviating the Fe-deficiency response and downregulating the expressions of Fe-uptake genes under alkaline conditions. In conclusion, alkaline stress inhibits NR activity and NO production in the roots of rice, which play vital roles in the mobilization of the apoplast Fe by regulation of H2 O2 and phenolic acid concentrations.

中文翻译：

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碱性条件下抑制一氧化氮产生调节水稻铁稳态

在中性和碱性条件下，水稻是最容易缺铁 (Fe) 的植物之一。碱性胁迫诱导H2O2产生并增加根表面Fe的沉积，导致水稻叶片萎黄和缺铁。基因芯片和 qRT-PCR 分析表明，硝酸还原酶 (NR) 基因的表达被碱处理下调，导致表皮和中柱中硝酸盐活性和一氧化氮 (NO) 的产生显着降低，其中 H2 O2 积累。相比之下，硝普钠 (SNP) 是一种 NO 供体，通过限制 Fe 斑块的形成，强烈缓解了碱诱导的 Fe 缺乏症。在碱性条件下，增加 NO 信号显着减少了 H2 O2 的积累和木质素屏障，但增强了根表皮和中柱中酚酸的分泌。分泌的酚酸有效地动员了质外体铁并增加了根对铁的吸收，从而减轻了缺铁反应并下调了碱性条件下铁吸收基因的表达。总之，碱性胁迫抑制了水稻根部的 NR 活性和 NO 的产生，这在通过调节 H2 O2 和酚酸浓度来动员质外体 Fe 中起着至关重要的作用。从而减轻缺铁反应并下调碱性条件下铁摄取基因的表达。总之，碱性胁迫抑制了水稻根部的 NR 活性和 NO 的产生，这在通过调节 H2O2 和酚酸浓度来动员质外体 Fe 中起着至关重要的作用。从而减轻缺铁反应并下调碱性条件下铁摄取基因的表达。总之，碱性胁迫抑制了水稻根部的 NR 活性和 NO 的产生，这在通过调节 H2 O2 和酚酸浓度来动员质外体 Fe 中起着至关重要的作用。