AhDi19-3B confers drought tolerance in peanut: Functional characterization of a candidate gene from the genome-wide identified Di19 family

Drought is a major abiotic constraint limiting peanut (Arachis hypogaea) production, yet the molecular mechanisms underlying stress adaptation remain poorly understood. The Drought-Induced 19 (Di19) gene family encodes C2H2-type zinc finger proteins implicated in abiotic stress responses, but their roles in peanut have not been systematically examined. In this study, a genome-wide analysis identified 16 Di19 genes distributed across ten chromosomes. Phylogenetic classification grouped these genes into five groups, while gene duplication analysis revealed that segmental duplication was the main driver of family expansion, with most duplicated pairs subjected to purifying selection. Conserved motif and exon-intron analyses indicated both structural conservation and functional divergence. Promoter regions were enriched with cis-elements responsive to abscisic acid, drought, and heat, and several family members were predicted to be regulated by peanut-specific miRNAs. Transcriptome-based expression profiling demonstrated distinct tissue-specific patterns and differential regulation under abiotic stress conditions. Time-course qRT-PCR analysis under combined drought and salinity stress revealed strong induction of AhDi19-3B . Subcellular localization confirmed the nuclear targeting of AhDi19-3B , and functional assays in transgenic Arabidopsis showed that its overexpression enhanced drought tolerance through improved water retention and reduced oxidative damage. These findings provide the first comprehensive characterization of the Di19 gene family in peanut and establish AhDi19-3B as a key regulator of drought tolerance. This work offers a foundation for future functional studies and highlights the translational potential of Di19 genes in developing stress-resilient peanut cultivars.