Genome-wide identification, evolutionary dynamics, and abiotic stress response networks of the magnesium transporter gene family in foxtail millet (Setaria italica L.)

Abstract

Magnesium (Mg²+) is an essential mineral nutrient for plant growth, playing a pivotal role in chlorophyll biosynthesis, enzyme activation, photosynthesis, and ion homeostasis. The magnesium transporters (MGTs) from the CorA/MRS2-ALR superfamily are crucial for Mg²+ uptake, translocation, and subcellular compartmentalization. Foxtail millet (Setaria italica L.), recognized as a drought-tolerant C4 cereal with a streamlined genome and robust environmental adaptability, presents an optimal model for investigating stress resilience and C4 photosynthesis. To date, the MGT gene family in foxtail millet has not been characterized. In this study, we identified nine SiMGT genes (SiMGT1–SiMGT9) through comprehensive genome-wide screening. These genes are distributed unevenly across chromosomes 4, 5, 7, and 9. Each SiMGT possesses conserved CorA domains and displays unique physicochemical attributes and subcellular localization patterns. Phylogenetic assessments categorized the SiMGTs into five distinct groups, indicating a close evolutionary relationship with graminaceous crops such as rice, maize, and sorghum, and suggesting functional conservation. Expression profiling highlighted that SiMGT1, SiMGT3, SiMGT6, SiMGT7, and SiMGT8 are consistently highly expressed. Notably, SiMGT7 is predominantly expressed in leaves, suggesting a potential association with leaf-related or photosynthesis-associated processes, while SiMGT6 shows preferential expression in panicles, indicating a possible role in reproductive development. When subjected to drought, low temperature, salinity, and ABA treatments, the SiMGTs exhibited varied temporal response patterns: SiMGT7 and SiMGT9 showed relatively strong responses to drought and cold stress; SiMGT2 responded prominently to salt treatment; and SiMGT1, SiMGT2, and SiMGT3 were rapidly induced at the early stage of ABA treatment. Haplotype analysis pinpointed superior haplotypes (Hap1) of both SiMGT6 and SiMGT7, which showed significant associations with panicle yield traits and stress-related traits, respectively. These findings provide insights into the evolutionary characteristics and expression divergence of the SiMGT family and offer candidate genes and molecular markers for future functional studies and the genetic improvement of foxtail millet.