Genome-Wide Identification and Expression Profiling of Dehydration-Responsive Element-Binding Family Genes in Flax (Linum usitatissimum L.)

Dehydration-responsive element-binding (<i>DREB</i>) transcription factors are ubiquitous in plants and regulate plant growth, development, signal transduction, and responses to stress, particularly drought stress. However, <i>DREB</i> genes in flax have not previously been studied. This study conducted a comprehensive and systematic analysis of the <i>DREB</i> gene family in flax (<i>Linum usitatissimum</i> L.). A total of 59 <i>LuDREB</i> genes were identified in Longya-10 (a breeding variety), with an uneven distribution across all 15 chromosomes. Further analysis revealed significant variations among LuDREB members, with predictions indicating that these proteins are hydrophilic and localized in the nucleus and cytoplasm. A phylogenetic analysis classified the <i>LuDREB</i> genes into six subgroups, a classification further supported by gene structure and motif composition. Members within the same subgroup exhibited structural conservation, suggesting functional redundancy. The duplication analysis identified 30 pairs of segmentally duplicated <i>LuDREB</i> genes and one pair of tandemly duplicated genes, indicating that segmental duplication was the primary driver of <i>LuDREB</i> gene expansion. A comparative collinearity analysis revealed that most <i>LuDREB</i> genes had orthologs in other plant species, suggesting that this gene family has remained relatively conserved throughout evolution. <i>Cis</i>-acting element analysis identified numerous hormone- and stress-responsive elements in <i>LuDREB</i> promoters, and the quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) results confirmed the role of all <i>LuDREB</i> genes in drought stress response. In addition, transcriptome analysis revealed that <i>LuDREB49</i> and <i>LuDREB56</i> exhibited high expression levels in the capsules, whereas <i>LuDREB3</i> and <i>LuDREB36</i> showed significantly higher expression levels in the stems, suggesting that these <i>LuDREB</i> genes may have specialized functions in capsule or stem development. Collectively, this study provides a comprehensive overview of <i>LuDREB</i> genes, offering valuable insights into their roles in flax growth, development, and stress responses.