Molecular identification of the magnesium transporter (MRS2/MGT) family genes in pepper (Capsicum annuum L.)

Magnesium (Mg2+) is the most prevalent divalent cation in plant cells, yet its transport machinery remains uncharacterised in pepper (Capsicum annuum L.), a globally important vegetable crop that is highly sensitive to Mg2+ deficiency. Here we report the genome-wide identification and functional annotation of nine MRS2/MGT-type Mg2+ transporter genes (CaMGTs) in the reference cultivar CM334. Phylogenetic analysis of these CaMGTs resolved five orthologous clades that mirror the evolutionary structure previously established for Arabidopsis thaliana and Oryza sativa. All CaMGTs harbour the CorA domain and the Mg2+-selective GMN motif. Heterologous complementation of the Mg2+-transport-deficient Salmonella typhimurium mutant MM281 demonstrated that each CaMGT restored growth under Mg2+ limitation, albeit with divergent apparent affinities: CaMGT10 ≥ CaMGT7 > CaMGT4.1 ≈CaMGT6 ≫ remaining isoforms. Quantitative RT-PCR revealed tissue-biased expression—CaMGT10 in leaves, CaMGT3/4.2 in roots—and rapid transcriptional reprogramming under Mg²⁺starvation. Promoter cis-element profiling further predicted integration of light, hormone and stress signals, consistent with the observed differential induction patterns. Collectively, our findings establish that CaMGT family as a versatile and evolutionarily conserved Mg²⁺transport system that underpins Mg²⁺uptake, translocation and cellular homeostasis in Capsicum annuum. This data provide a molecular foundation for future functional characterization and breeding applications.