Genomic and Functional Characterization of the Phenylalanine Ammonia Lyase (PAL) Gene Family in Wheat ( <i>Triticum aestivum</i> ) Reveals Roles in Salt Stress Adaptation

Plant phenylpropanoid metabolism is a crucial process involving phenylalanine ammonia lyase (PAL) enzyme, which is essential for plant growth and development. PAL generates secondary metabolites and also has a significant impact on plant defense against disease and stress. Salt stress is a common abiotic stress that severely impacts wheat growth and restricts its productivity worldwide. However, genome-wide and functional characterization of the PAL gene family in wheat is limited. In this study, 54 PAL genes were identified in wheat, distributed across 15 chromosomes, with one located on an unknown chromosome. The analysis of gene structures, conserved motifs, duplication events, and cis-acting elements was performed to understand their functional diversity. Phylogenetic analysis classified wheat PAL proteins into nine subfamilies, highlighting evolutionary diversification specific to monocots. Additionally, evolutionary analysis of PAL genes in Triticum aestivum, Triticum turgidum, and Aegilops tauschii grouped them into six subgroups. Promoter analysis indicated that TaPAL genes contain multiple cis-regulatory elements associated with stress, growth, hormonal regulation, and light response. TaPAL genes displayed dynamic expression profiles across different tissues and developmental stages, and were significantly regulated under various stress conditions. Quantitative real-time PCR (qRT-PCR) analysis revealed the expression patterns of TaPAL genes under salt stress, indicating their potential role in abiotic stress response. These findings provide valuable insights into the evolutionary and functional significance of PAL genes in wheat, offering a foundation for future research on their role in stress tolerance and crop improvement.