THE ROLE OF MUGINEIC ACID IN UPTAKE OF TRACE METALS IN PLANTS

Project Information

MAZinc

Grant agreement ID: 101032337

DOI

10.3030/101032337

Project closed

EC signature date 27 April 2021

Start date 22 November 2021

End date 21 April 2025

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 319 400,64

EU contribution

€ 319 400,64

Coordinated by

IMPERIAL COLLEGE OF SCIENCE TECHNOLOGY AND MEDICINE
United Kingdom

Periodic Reporting for period 1 - MAZinc (THE ROLE OF MUGINEIC ACID IN UPTAKE OF TRACE METALS IN PLANTS)

Reporting period: 2021-11-22 to 2024-11-21

Summary of the context and overall objectives of the project

The MAZinc project addressed the urgent issue of zinc (Zn) deficiency in agricultural soils, a problem affecting approximately 50% of soils worldwide and severely compromising crop yield and nutritional quality, especially in rice-growing regions. This deficiency poses a grave threat to human health, particularly in areas where rice is a staple food, leading to hidden hunger and serious health issues such as impaired neurobehavioral development, reproductive health problems, and increased vulnerability to infectious diseases like pneumonia.
Improving our understanding of the key mechanisms involved in Zn uptake in rice is central to developing strategies to mitigate Zn deficiency in food and to prevent human malnutrition.
The aim of this fellowship was to better understand the role siderophores play in this process, and in particular how Zn is complexed and taken up in rice by deoxymugineic acid (DMA). To achieve this, we identified three distinct but inter-related objectives:
1) to develop analytical protocols to enable accurate determination of DMA in rice soil solution
2) to quantify DMA secretion rate to identify its environmental controls
3) to establish stability series for DMA with all the key micronutrient metals to test the stability of Zn-DMA in soil solution and plants

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

1) A robust analytical protocol was developed to accurately measure DMA in rice soil solutions using HPLC-LC/Q TOF system. This method enhances sensitivity and reproducibility for polar acidic metabolites like DMA, enabling reliable detection even at low concentrations. Mass spectrometry detected DMA with major peaks at [M-H]- 303.1198 m/z, consistent with literature. A rice pilot experiment showed increased DMA secretion in rice grown under nutrient deficiency. The method proved to be simple and highly sensitive for detecting DMA in root exudates.
2) Hydroponic experiments with five rice genotypes, including Zn-deficiency tolerant and intolerant varieties, revealed a 0.5- to 3.6-fold increase in DMA secretion under Zn-deficient conditions compared to controls. Sensitive genotypes also showed increased DMA exudation, suggesting a direct role for DMA in the rice response to Zn deficiency.
3) To investigate Zn-DMA interactions, proline-2′-deoxymugineic acid (PDMA), a synthetic ligand analogue to DMA produced by Aichi Steel Corporation, was used as a practical model compound. PDMA is chemically stable and more cost-effective to synthesize than natural DMA. Potentiometric titrations and thermodynamic speciation calculations show that PDMA forms stable complexes with Zn in soil solutions with pH from 6 to 9, showing similar behaviour to natural ligands like DMA. PDMA was then evaluated as a potential Zn fertilizer for paddy soils. Geochemical models showed that PDMA preferentially binds with Cu and Fe in oxidized conditions and with Zn in reduced conditions. The project identified optimal conditions to maximize PDMA efficacy. Considering paddy soil parameters (pH, redox potential, and salinity), PDMA should be applied in flooded soil at pH 7 - 9 or as complexed Zn-PDMA in flooded and aerated soil. This is a promising strategy to mitigate Zn deficiency in soil, enhancing rice nutrition and reducing human malnutrition. The collaboration with Aichi Steel helped us avoid the complex and costly synthesis of DMA and advance the application of synthetic, eco-friendly molecules inspired by natural ligands like DMA, to enhance Zn availability in agricultural soils.
This project made significant strides in addressing Zn deficiency in rice soils by enabling accurate DMA measurement, demonstrating that Zn deficiency increases DMA secretion in rice, and exploring the potential of PDMA as a stable, cost-effective alternative to enhance Zn availability in soil.
MAZinc project results have been disseminated through poster, oral communication at conferences, preprint and scientific articles in peer-reviewed journals

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Throughout the duration of the project, significant progress was made in understanding the role of DMA in Zn deficiency condition.

1) The successful development of the LC-MS/MS technique significantly advanced our ability to detect DMA in solution with high precision and sensitivity, enabling detailed study on DMA response under nutrient deficiency.
2) Beyond rice, the method is applicable to other cereals, supporting comparative studies of siderophore secretion under Zn deficiency. It also allows for detailed investigation of DMA-metal complexation under varying soil conditions. These insights are crucial for designing next-generation fertilizers like PDMA to improve nutrient efficiency and agriculture sustainability. Hydroponic experiments provided critical insights into rice responses to Zn deficiency, revealing a significant increase in DMA secretion under Zn-deficient conditions, even in Zn-sensitive varieties, compared to controls. This research advances our understanding of DMA secretion under Zn deficiency, supporting breeding programs aimed at developing rice varieties with enhanced Zn uptake, improving crop yields, nutritional quality, and addressing Zn deficiency in plants and humans.
3) The relevance of this project in addressing Zn deficiency in agriculture led to a collaboration with Aichi Steel to investigate PDMA as a Zn fertilizer. PDMA forms stable complexes with Zn, particularly under reducing and alkaline conditions, which are typical of flooded paddy soils, demonstrating its potential as fertilizer to overcome Zn deficiencies. The application of PDMA can significantly enhance food security and reduce malnutrition, especially in regions where rice is a staple food. Its DMA-based structure makes it an eco-friendly alternative for Zn fertilization, minimizing the risk of long-term soil contamination. Its production is easier and cheaper compared to DMA and is more resistant to microbial decomposition. This can optimize fertilization practices, reduce environmental impact, and promote sustainable agriculture. These findings pave the way for developing new eco-sustainable fertilizers based on DMA uptake mechanisms. MAZinc project outcomes have the potential to open new market for eco-sustainable fertilizers and mitigate environmental impacts of conventional fertilization.

Aichi Steel Corporation is actively working to commercialize PDMA, primarily focusing on Fe due to its core business. This research expanded the applications of PDMA beyond iron, demonstrating its potential in enhancing Zn absorption. This work advances knowledge critical to breeding Zn-efficient rice, improving nutrient uptake.
Geochemical analysis of siderophores-Zn complexation, hydroponic experiment and DMA detection provided the evidence of DMA involvement in rice response to Zn deficiency.
The socio-economic impact includes improved food security, enhanced agricultural productivity, and contributing to global efforts to solve food security challenges.
This research has strong potential to impact agriculture by addressing environmental challenges and promoting efficient nutrient management. PDMA-based fertilizers offer an eco-friendly alternative that reduces excessive fertilizer use and minimize runoff into water. Modelling metal-ligand interactions in soil supports precision agriculture through site-specific nutrient strategies. These advancements will strengthen the competitiveness of companies working in sustainable crop nutrition, contributing to mitigate Zn deficiency in humans

Illustration of MAZinc work