Genome-Wide Identification of the Dirigent Gene Family and Expression Pattern Analysis Under Drought and Salt Stresses of (L.).

The () gene family is pivotal for lignin polymerization and stress adaptation in plants, yet its systematic characterization in (), a critical bioenergy crop, remains underexplored. Leveraging the genome database, we conducted a genome-wide identification, phylogenetic classification, and expression profiling of the gene family. Evolutionary dynamics, gene structure variations, promoter cis-regulatory elements, and spatiotemporal transcriptome patterns were analyzed using bioinformatics and experimental validation (RT-qPCR). A total of 53 genes were systematically identified, exhibiting uneven chromosomal distribution. Phylogenetic analysis clustered them into five clades (DIR-a, DIR-b/d, DIR-c, DIR-e, DIR-f), with subfamily-specific exon number variations suggesting functional divergence. Evolutionary studies revealed tandem duplication (TD) as the primary driver of family expansion, accompanied by strong purifying selection. Promoter analysis highlighted abundant hormone- and stress-responsive cis-elements. Tissue-specific RNA-seq data revealed root-enriched expression of , implicating their roles in root development. Notably, and were significantly upregulated (2.8- and 5-fold, respectively) under 150 mM NaCl stress, underscoring their stress-responsive functions. This study provides the first comprehensive atlas of the gene family in , elucidating its evolutionary mechanisms and tissue-specific/stress-induced expression profiles. Key candidates () were identified as promising targets for molecular breeding or CRISPR-based editing to enhance stress resilience in . These findings lay a foundation for translating genomic insights into agronomic improvements.