# Overexpression of GmCSY3 Enhances Soybean Tolerance to Excess Iron and Aluminum

## TL;DR

Overexpression of the GmCSY3 gene in soybeans helps plants tolerate high levels of iron and aluminum, reducing damage and improving growth in acidic soils.

## Contribution

The study identifies GmCSY3 as a key gene in citric acid synthesis that enhances soybean tolerance to excess iron and aluminum stress.

## Key findings

- GmCSY3 overexpression increases citrate synthase activity and reduces oxidative damage from excess Fe and Al.
- RNAi suppression of GmCSY3 leads to reduced citrate synthase activity and increased plant damage under Fe or Al stress.
- GmCSY3 helps chelate Fe3+ and Al3+, modulating iron absorption and improving plant resilience.

## Abstract

Plants growing in acidic soil are prone to poisoning from excessive Fe or Al, which can lead to growth damage. We obtained the GmCSY3 gene of soybean, which is involved in the synthesis of citric acid. The expression of GmCSY3 became more active when soybean roots were exposed to high levels of Fe or Al. Experiments demonstrated that increasing the expression level of GmCSY3 enhanced the activity of citrate synthase, which subsequently binds to excess Fe and Al, resulting in reduced damage in plants exposed to excessive Fe and Al. Conversely, reducing the expression level of GmCSY3 in plants reduced citrate synthase activity and caused greater harm to the plants. Understanding the process involved in this GmCSY3 gene can help develop more resistant crops or new application supplements to better cope with acidic or contaminated soil, contributing to better food production.

Background: Plant citrate synthase (CSY) is involved in the iron deficiency (−Fe) response and aluminum (Al) detoxification. However, knowledge of CSY function in responding to excess iron (+Fe) or Al stress (+Al) is still limited. Methods: The CDS and promoter of GmCSY3 were isolated from soybean and bioinformatically analyzed. The GmCSY3 expression was detected by qRT-PCR and GUS assay. The growth of GmCSY3 recombinant yeast under +Fe or +Al was detected. The phenotype, CSY activity, citric acid concentration, chlorophyll content, MDA, H2O2, O2− contents, GST, CAT, SOD, and POD activities were examined in GmCSY3 overexpressed and RNAi-suppressed soybean chimeras under +Fe or +Al. Perls and Hematoxylin stained the roots, and the FCR activity was determined. Results: GmCSY3 was induced by +Fe or +Al, but not by −Fe. GmCSY3 enhanced yeast’s acid production and resistance to +Fe or +Al. GmCSY3 overexpression in soybean significantly enhanced CSY activity, promoted growth, alleviated oxidative damage caused by +Fe or +Al, with less free Fe3+ and Al3+, and reduced FCR activity, while GmCSY3 RNAi-suppressed showed the opposite effect. Conclusions: GmCSY3 promotes the process of citrate synthesis, chelates Fe3+ and Al3+, alleviates oxidative damage caused by +Fe or +Al, and modulates iron absorption in plants.