Genome-Wide Identification and Functional Characterization of the Dof Gene Family in Flax (Linum usitatissimum)

DNA-binding with one finger (Dof) transcription factors are plant-specific regulators of growth, development, and stress responses. Despite extensive characterization in various species, Dof genes in flax (Linum usitatissimum L.), an important oil and fiber crop, remain largely uncharacterized. Through genome-wide identification and comprehensive characterization of the Dof gene family in flax, this study identified 47 LuDof genes in the high-oil Longya-10 variety, distributed non-uniformly across 15 chromosomes. Phylogenetic analysis grouped these genes into 12 distinct clusters, reflecting evolutionary conservation and lineage-specific characteristics, including the absence of LuDof members in Group XII. Gene structure and conserved motif analyses revealed strong structural conservation, particularly within the canonical zf-Dof domain. Segmental duplication was identified as the primary driver of LuDof family expansion, with all paralogous pairs evolving under strong purifying selection. Collinearity analysis revealed that 80.9% of LuDof genes have homologs in other species, highlighting strong evolutionary conservation. Promoter analysis identified multiple hormone- and stress-responsive elements, and qRT-PCR under drought, heat, cold, and methyl jasmonate (MeJA) treatments confirmed their roles in environmental stress responses. Transcriptome profiling indicated their involvement in stem and capsule development. This study represents the first systematic characterization of the evolution, structure, and functional potential of the flax Dof gene family, establishing a foundation for functional studies and for developing genetically superior, stress-tolerant flax varieties.