Evers Anna, Kohn Jackson, Baars Oliver, Harrington James M, Namba Kosuke, Duckworth Owen W
Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, 27695, USA.
Department of Geology, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO, 80903, USA.
Biometals. 2024 Dec;37(6):1599-1607. doi: 10.1007/s10534-024-00629-7. Epub 2024 Aug 28.
Adequate micronutrient concentrations in crops are essential for human health and agricultural productivity. However, 30% of plants growing on cultivated soils worldwide are deficient in iron (Fe). Because of low micronutrient bioavailability, graminaceous plants have evolved to exude small molecules, called phytosiderophores, into the soil environment, which strongly complex and promote uptake of trace elements. The development of a synthetic phytosiderophore, proline-2'-deoxymugeneic acid (PDMA), has been shown to promote Fe uptake in rice plants; however, its binding capabilities with other metals, which may impact the ability to promote the uptake of Fe and other trace nutrient metals commonly found in soils, remain unknown. We conducted spectrophotometric titrations to determine the stability constants (logK) of PDMA complexes with Mn(II), Co(II), Cu(II), Ni(II), and Zn(II). We determined that PDMA complex stability constants correlated with: (1) the hydrolysis constants of metal ions (logK) in complexes; (2) the ionic potential of complexed metals; and (3) the corresponding complex stability constants of other mugineic acid type phytosiderophores, as well as the trishydroxamate microbial siderophore DFOB. These correlations demonstrate the potential, and limitations, on our ability to predict the stability of phytosiderophore complexes with metal ions with different physicochemical properties and with potentially different coordination structures.
作物中充足的微量营养素浓度对人类健康和农业生产力至关重要。然而，全球耕地上生长的植物中有30%缺铁（Fe）。由于微量营养素的生物有效性低，禾本科植物进化出向土壤环境中分泌称为植物铁载体的小分子，这些小分子能强烈络合并促进微量元素的吸收。合成植物铁载体脯氨酸 - 2'-脱氧麦根酸（PDMA）已被证明能促进水稻对铁的吸收；然而，它与其他金属的结合能力，可能会影响促进铁和土壤中常见的其他微量营养金属吸收的能力，仍然未知。我们进行了分光光度滴定，以确定PDMA与Mn(II)、Co(II)、Cu(II)、Ni(II)和Zn(II)络合物的稳定常数（logK）。我们确定PDMA络合物的稳定常数与以下因素相关：（1）络合物中金属离子的水解常数（logK）；（2）络合金属的离子势；（3）其他麦根酸型植物铁载体以及三羟基肟酸微生物铁载体DFOB的相应络合物稳定常数。这些相关性证明了我们预测具有不同物理化学性质和潜在不同配位结构的植物铁载体与金属离子络合物稳定性的能力的潜力和局限性。
