Wang Baolan, Wei Haifang, Chen Zhuo, Li Yuting, Zhang Wen-Hao
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, PR China.
College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
Plant Cell Physiol. 2022 Jun 15;63(6):770-784. doi: 10.1093/pcp/pcac038.
Significant progress has been made in understanding Strategy I iron (Fe) acquisition using crop/model plants under controlled conditions in laboratories. However, plant species native to calcareous soils may have evolved unique strategies for adaptation to high carbonate/pH-induced Fe deficiency. Until now, little information is available on the Fe acquisition mechanisms in these plants. Here, we explored the Fe acquisition mechanisms in wild dicot species native to calcareous grasslands, by monitoring the Fe nutrition-related rhizosphere processes in field and greenhouse conditions. Most of these wild species displayed comparable shoot Fe concentration to those of crops, and some dicots actually accumulated very high shoot Fe. However, these species did not exhibit ferric reductase oxidase (FRO)-dependent Strategy I responses to Fe deficiency, including visual rhizosphere acidification and increased Fe3+ reduction. In contrast, chemical reductants exuded by roots of dicots were responsible for Fe3+ reduction in these wild plants. These features were not observed in the FRO-dependent Strategy I crop plant cucumber. Neither leaf chlorophyll nor shoot/root Fe was depressed by 10% CaCO3 application in all the examined wild species. Furthermore, their root exudation was significantly activated by CaCO3, leading to an increased Fe3+ reduction. We show that chemical reductant-mediated Fe3+ reduction occurs preferentially in these wild dicots and that these mechanisms are not sensitive to high soil carbonate/pH. Our findings support that Fe acquisition in Strategy I wild plants native to calcareous soils is substantially different from the enzyme-dependent system of Strategy I plants.
在实验室可控条件下，利用农作物/模式植物研究策略I铁（Fe）吸收方面已取得显著进展。然而，原产于石灰性土壤的植物物种可能已经进化出独特的策略来适应高碳酸盐/ pH值诱导的铁缺乏。到目前为止，关于这些植物中铁吸收机制的信息很少。在这里，我们通过监测田间和温室条件下与铁营养相关的根际过程，探索了原产于石灰性草原的野生双子叶植物物种的铁吸收机制。这些野生物种中的大多数地上部铁浓度与作物相当，一些双子叶植物实际上积累了非常高的地上部铁。然而，这些物种在缺铁时并未表现出依赖于铁还原酶氧化酶（FRO）的策略I反应，包括可见的根际酸化和Fe3+还原增加。相反，双子叶植物根系分泌的化学还原剂负责这些野生植物中的Fe3+还原。在依赖FRO的策略I作物黄瓜中未观察到这些特征。在所有检测的野生物种中，施用10% CaCO3均未降低叶片叶绿素或地上部/根部铁含量。此外，它们的根系分泌物被CaCO3显著激活，导致Fe3+还原增加。我们表明，化学还原剂介导的Fe3+还原优先发生在这些野生双子叶植物中，并且这些机制对高土壤碳酸盐/ pH值不敏感。我们的研究结果支持，原产于石灰性土壤的策略I野生植物中的铁吸收与策略I植物的酶依赖系统有很大不同。
