Genome-wide profiling of GRAS genes in flax (Linum usitatissimum L.) reveals LuGRAS30 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 LuGRAS 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 LuGRAS genes within the same clade exhibited conserved exon-intron organization and motif architectures. Promoter analysis showed that most LuGRAS 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 LuGRAS gene family. Expression pattern analysis demonstrated that all LuGRAS 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 Arabidopsis, LuGRAS30 enhanced drought tolerance by scavenging reactive oxygen species (ROS) accumulation. Subcellular localization analysis demonstrated that LuGRAS30 was localized in the nucleus. This study provides new insights into the role of LuGRAS genes in flax stress tolerance and contributes to flax breeding and further functional research.