Genome-wide profiling of GRAS genes in flax ( <i>Linum usitatissimum</i> L.) reveals <i>LuGRAS30</i> as a key regulator of drought stress resistance

GRAS genes are indispensable for modulating plant growth, developmental patterning, and adaptive responses to biotic and abiotic stress conditions. In this study, 99 <i>LuGRAS</i> genes were identified in the flax genome. Phylogenetic analysis classified them into 10 subfamilies: HAM, DELLA, DLT, SCL3, LAS, SCL4/7, SCR, SCL, SHR, and PAT1. Gene structure and motif analyses revealed that <i>LuGRAS</i> genes within the same clade exhibited conserved exon-intron organization and motif architectures. Promoter analysis showed that most <i>LuGRAS</i> genes contained cis-regulatory elements responsive to plant hormones (MeJA and abscisic acid) and abiotic stresses, including anaerobic induction, low temperature, and drought inducibility. MiRNA target prediction indicated that lus-miR395 is the primary regulatory miRNA for the <i>LuGRAS</i> gene family. Expression pattern analysis demonstrated that all <i>LuGRAS</i> family members were highly expressed in leaves and roots. qRT-PCR analysis further revealed that 10 genes were significantly upregulated under abiotic stresses (cold, drought, and salt), suggesting their involvement in antioxidant defense mechanisms. In <i>Arabidopsis</i>, <i>LuGRAS30</i> enhanced drought tolerance by scavenging reactive oxygen species (ROS) accumulation. Subcellular localization analysis demonstrated that <i>LuGRAS30</i> was localized in the nucleus. This study provides new insights into the role of <i>LuGRAS</i> genes in flax stress tolerance and contributes to flax breeding and further functional research.