Comparative analysis of the GRAS transcription factor family in oilseed and confectionery sunflower identifies HaGRAS19 as a regulator of salt stress responses

Sunflower ( Helianthus annuus L.) is a globally important oilseed crop known for its resilience to environmental stresses. GRAS transcription factors are pivotal regulators of plant development and stress responses. However, a comprehensive analysis of this family in the economically distinct oilseed and confectionery sunflowers is lacking. Here, we performed a genome-wide comparative analysis and identified 98 GRAS genes in both the oilseed and confectionery sunflower genomes. Phylogenetic analysis delineated a novel, sunflower-specific subfamily, FDSLD, defined by a unique conserved motif. Comparative genomics further revealed type-specific differences in gene composition. For instance, the oilseed sunflower harbors five DELLA genes, whereas the confectionery type contains four. Evolutionary rate analysis indicated that the GRAS family has undergone strong purifying selection, highlighting its functional conservation. Based on cis -regulatory element analysis, we profiled the expression of GRAS genes potentially involved in hormone and stress responses. Functional characterization through transient silencing assays demonstrated that HaGRAS19 is critical for salt stress adaptation. Specifically, it eliminates salt-induced oxidative damage by reducing reactive oxygen species (ROS) accumulation and malondialdehyde (MDA) production. Mechanistically, we identified a HaGRAS19- HaSnRK2.2 / 2.4.3 regulatory module. HaGRAS19 directly binds to the promoters of HaSnRK2.2 and HaSnRK2.4.3 . This binding activates ABA-dependent signaling pathways, supported by the quantitative regulation of downstream marker genes ( HaABI2 , HaEM6 , and HaRD26 ). This study provides the first comprehensive comparative genomic resource for the sunflower GRAS family. Furthermore, the characterization of this novel regulatory module offers both fundamental insights into stress adaptation and promising targets for breeding resilient sunflower cultivars. • First comparative analysis of the GRAS transcription factor family in oilseed and confectionery sunflower types , identifying 98 GRAS genes and revealing a novel sunflower-specific FDSLD subfamily. • Evolutionary analyses reveal strong purifying selection and type-specific differences in DELLA gene copy number. • 3. HaGRAS19 is functionally characterized as a key salt-stress regulator, whose silencing compromises oxidative stress tolerance and water retention. • Elucidation of a HaGRAS19–SnRK2 module , where HaGRAS19 transcriptionally activates HaSnRK2.2 and HaSnRK2.4.3 to potentiate ABA-dependent signaling.