<p class="MsoNormal" align="justify" style="text-align:justify;"> 质子响应的<i>SlSTOP1-SlFRDL1</i>调控通路介导番茄根部柠檬酸依赖性的铁吸收

Journal of Integrative Agriculture ›› 2026, Vol. 25 ›› Issue (9): 3703-3714.DOI: 10.1016/j.jia.2025.12.072

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质子响应的SlSTOP1-SlFRDL1调控通路介导番茄根部柠檬酸依赖性的铁吸收

收稿日期:2025-04-19 修回日期:2025-12-31 接受日期:2025-09-25 出版日期:2026-09-20 发布日期:2026-08-10

Proton-responsive SlSTOP1–SlFRDL1 regulatory pathway modulates citrate-driven iron acquisition in tomato roots

Huihui Zhu^1*, Liqiong Jia^1*, Yuzhi Bai¹, Junqiang Xu¹, Xulu Luo¹, Wei Fan¹, Weiwei Chen^2#, Jianli Yang^1#

¹Key Laboratory of Vegetable Biology of Yunnan Province, College of Landscape and Horticulture, Yunnan Agricultural University, Kunming 650201, China
²College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China

Received:2025-04-19 Revised:2025-12-31 Accepted:2025-09-25 Online:2026-09-20 Published:2026-08-10
About author:#Correspondence Jianli Yang, E-mail: yangjianli@zju.edu.cn; Weiwei Chen, E-mail: 15858223807@163.com *These authors contributed equally to this study.
Supported by:
This work was financially supported by the Joint Agricultural Project of Department of Science and Technology of Yunnan Province, China (202401BD070001-010), the National Natural Science Foundation of China (32372803) and the Science and Technology Major Project of Yunnan Province Science and Technology Department, China (202502AE090025 to J. Y.).

摘要/Abstract

摘要：

在根际铁活化过程中，环境pH条件对根系分泌物的组成与功能具有决定性影响。尽管有机酸在铁溶解过程中的作用已得到广泛证实，但其pH依赖性的分子调控机制仍存在认知空白。本研究揭示了弱酸性环境（pH 5.0-6.0）下根系铁活化的新机制。研究发现，在该pH范围内，根系分泌的质子单独作用难以有效溶解难溶性铁，必须依赖pH敏感的有机配体协同作用。比较分析显示，柠檬酸相较于草酸和苹果酸具有显著更高的铁溶解效率。分子机制研究表明，质膜定位的柠檬酸转运蛋白SlFRDL1是这一过程的关键执行者。缺铁胁迫显著诱导SlFRDL1基因表达，其敲除突变体Slfrdl1因柠檬酸分泌缺陷而表现出加重的缺铁黄化表型。进一步研究发现，转录因子SlSTOP1通过特异性结合SlFRDL1启动子区域来激活其表达。遗传证据显示，Slstop1突变体与Slfrdl1突变体具有高度相似的缺铁敏感表型，证实二者在功能上存在协同关系。特别值得注意的是，与FER介导的广谱pH适应型铁吸收系统不同，SlSTOP1-SlFRDL1模块表现出严格的pH依赖性调控特征——仅在酸性条件下被缺铁信号特异性激活。这一发现不仅阐明了酸性土壤中铁活化的分子基础，也为作物适应不同pH环境的铁营养调控机制提供了新的理论依据。

Abstract:

The composition and function of root exudates in rhizosphere iron (Fe) mobilization are significantly influenced by environmental pH conditions. While the role of organic acids in Fe solubilization is well-recognized, the molecular mechanisms underlying this pH-dependent process remain poorly understood. Here, we demonstrate that under weakly acidic conditions, proton excretion alone is insufficient to solubilize sparingly soluble Fe. Instead, a pH-dependent ligand specificity emerges as a critical factor in Fe mobilization. Notably, within the pH range of 5.0–6.0, citric acid exuded by roots exhibits superior Fe solubilization efficacy compared to oxalic acid and malic acid. We identified SlFRDL1, a gene induced by Fe deficiency, as a key player in this process. SlFRDL1 encodes a plasma membrane-localized protein with citrate permeability, as confirmed by its functional expression in Xenopus oocytes. Knockout mutants of SlFRDL1 displayed exacerbated Fe deficiency symptoms, which were associated with a significant reduction in citrate secretion from roots. Furthermore, we discovered that SlSTOP1, a transcription factor, binds to the promoter region of SlFRDL1 and activates its expression. Slstop1 mutants exhibited leaf chlorosis symptoms similar to those observed in Slfrdl1 mutants, highlighting the functional interplay between these two genes. Interestingly, while Fe deficiency triggers the FER-mediated Fe uptake system under both acidic and alkaline conditions, the SlSTOP1–SlFRDL1 module is specifically activated only in acidic environments. This pH-specific regulation underscores the importance of the SlSTOP1–SlFRDL1 pathway in root-mediated Fe solubilization under acidic conditions.

Key words: citrate exudation , iron (Fe) mobilization , pH , SlFRDL1 , SlSTOP1

Huihui Zhu, Liqiong Jia, Yuzhi Bai, Junqiang Xu, Xulu Luo, Wei Fan, Weiwei Chen, Jianli Yang.

质子响应的SlSTOP1-SlFRDL1调控通路介导番茄根部柠檬酸依赖性的铁吸收 [J]. Journal of Integrative Agriculture, 2026, 25(9): 3703-3714.

Huihui Zhu, Liqiong Jia, Yuzhi Bai, Junqiang Xu, Xulu Luo, Wei Fan, Weiwei Chen, Jianli Yang. Proton-responsive SlSTOP1–SlFRDL1 regulatory pathway modulates citrate-driven iron acquisition in tomato roots[J]. Journal of Integrative Agriculture, 2026, 25(9): 3703-3714.

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