Genome-Wide Identification and Functional Analysis of the ZIP Gene Family in Sugarcane Under Manganese Stress

Manganese toxicity severely restricts the growth and yield of sugarcane in acidic soil. However, the molecular mechanism of the specific tolerance of different genotypes to manganese remains unclear. This study aims to identify and functionally characterize the ZIP manganese transporter genes in sugarcane, and to elucidate the differences in manganese regulatory mechanisms between the sensitive type GT32 (Saccharum hybrid cultivar) and the tolerant type ZZ1 (Saccharum hybrid cultivar). Through phylogenetic analysis, conserved motifs and cis-acting element analysis, as well as Ka/Ks analysis, a total of 24 ZIP genes were identified in three different sugarcane genotypes. Combined with hydroponic manganese stress treatments, quantitative reverse transcription PCR (qRT-PCR), ion concentration measurements and chlorophyll analysis, physiological and transcriptional differences between ZZ1 and GT32 were compared. Yeast complementation experiments verified the manganese transport ability of ScIRT1 and ScZIP3. Under manganese stress conditions, the results showed that the chlorophyll content of ZZ1 was 41.14% higher than that of GT32, and the manganese accumulation in roots and stems was lower. Significant differences were also observed in the transcriptional patterns of ZIP genes in roots and stems. The qRT-PCR results indicated tissue-specific differences: the transcription level of ScZIP7 in the roots of GT32 was 10 times higher, while ZZ1 maintained the high transcription level of ScZIP3 under manganese stress. The genotype-dependent expression patterns of ScIRT1, ScZIP3, ScZIP6, and ScZIP7 may contribute to the regulation of manganese uptake and intracellular distribution, thereby contributing to the enhanced manganese tolerance observed in ZZ1. These findings provide valuable insights into the molecular basis of manganese tolerance and highlight potential candidate genes for the genetic improvement in manganese-tolerant sugarcane varieties.