Distinct Mg²⁺ responses and species-specific transcriptional regulation of the magnesium transporter MGR2 in Saccharum officinarum and Saccharum spontaneum.

backgroundMagnesium (Mg²⁺) is essential for chlorophyll synthesis, enzyme activation, and photosynthesis, but the differential regulation of Mg²⁺ homeostasis between the two founding Saccharum species (Saccharum officinarum and Saccharum spontaneum) remains unknown.

resultsWe systematically characterized the MGR gene family in S. spontaneum and S. officinarum and uncovered distinct physiological responses to Mg²⁺ availability between the two species. Comparative expression analysis across the leaf developmental gradient and diurnal cycles revealed species-specific transcriptional dynamics of MGR2, suggesting divergent regulatory mechanisms underlying Mg²⁺ management. Functional complementation in the Mg²⁺-deficient Salmonella typhimurium MM281 mutant demonstrated that both SsMGR2 and SoMGR2 restore Mg²⁺ uptake, confirming their conserved transport capability. Overexpression of SsMGR2 in rice conferred increased biomass under Mg²⁺ deficiency and enhanced tolerance to Mg²⁺ excess, indicating a broad role for this gene in Mg²⁺ homeostasis. Promoter architecture and transcription factor prediction further revealed interspecific divergence, with BBX25, COL5, and WRKY19-2 exhibiting species-dependent regulatory interactions that potentially explain the observed differences in MGR2 expression.

conclusionOverall, the research results indicate that S. spontaneum and S. officinarum exhibit different Mg²⁺ responses and MGR2 regulatory patterns, highlighting the distinct strategies for Mg²⁺ homeostasis in these two founding species. This work provides new insights into the transport mechanism of Mg²⁺ in sugarcane and preliminarily identifies candidate genes and regulatory factors for improving nutrient efficiency and stress recovery ability.