Discovery and characterization of magnesium transporter (MGT) gene family in Citrus sinensis and their role in magnesium deficiency stress

The divalent cation Magnesium (Mg 2+ ) is necessary for healthy plant development, growth, and defense. Plants acquire Mg 2+ from the soil and transport it throughout their body tissues with Mg 2+ transporter (MGT) proteins. Although several MGT genes have been discovered and described in rice, maize, and Arabidopsis , far less information is available regarding their diversity and function in other plant species. To address this knowledge gap, here we identified seven putative MGT genes ( CsMGT1 - CsMGT7 ) in Citrus sinensis , which were classified into four distinct clades through phylogenetic analysis. Gene structures, cis -acting regulatory elements, and conserved motifs were also analyzed. Quantitative real-time PCR (qRT-PCR) indicated that the seven CsMGT genes were constitutively expressed across a variety of plant tissues, with the exception of CsMGT5 , which lacked detectable expression in fruit peels and pulp. Furthermore, qRT-PCR indicated that the seven CsMGT genes responded differently to Mg 2+ deprivation in leaves and roots. Complementation assays using Salmonella typhimurium MM281 and yeast CM66 demonstrated that CsMGT7 possessed the strongest Mg 2+ transport capacity. We propose that CsMGT7 might serve as an Mg 2+ transporter and play a crucial role in Mg 2+ deficiency response. Our results will aid future research on the biological roles of MGT s in plants, which is beneficial for combining theoretical and application-based research in fruit plants.