Genome-wide identification of bZIP transcription factors and their role towards drought stress and fruit development in Mangifera indica (mango)

Context The basic leucine zipper (bZIP) transcription factor family plays vital roles in regulating growth, development, and responses to environmental stresses. Whereas bZIPs have been studied extensively in various crops, their roles in Mangifera indica (mango) remain largely unexplored. Aims This study aimed to perform the first genome-wide identification and functional characterization of bZIP transcription factors in mango, with a focus on their involvement in drought stress response and fruit development. Methods In total, 97 putative MibZIP genes were identified through homology-based searches and validated via domain analysis. Phylogenetic analysis grouped 91 confirmed bZIP genes into nine clades. Conserved motifs, protein properties, subcellular localization, and promoter cis-elements were analyzed. Expression profiles were examined using RNA-seq and validated through quantitative reverse transcription–polymerase chain reaction (qRT–PCR) under drought conditions in both roots and leaves. Key results Most MibZIP proteins were predicted to be hydrophilic and nuclear-localized. Ten conserved motifs were identified, with motif 1 present in nearly all proteins. Several MibZIPs contained additional domains (e.g. DOG1, MFMR, NB-ARC), indicating functional diversification. Promoter analysis showed 71 types of cis-regulatory elements. Expression profiling showed dynamic gene regulation under drought stress. Notably, MibZIP27.2 was consistently upregulated, whereas MibZIP29.2 and MibZIP53.1 were downregulated in leaf tissue; both MibZIP27.2 and MibZIP53.1 were also downregulated in roots. Conclusions This study offers the first comprehensive overview of the bZIP gene family in mango and their potential regulatory roles. Implications The findings have provided a foundation for functional genomics and breeding strategies to enhance drought resilience and fruit quality in M. indica.