Comprehensive Genome-Wide Characterization of the GRAS Gene Family and Their Role in Salt Stress Tolerance in Punica granatum L.

The GRAS gene family is broadly distributed in plants and plays key regulatory roles in development, signal transduction, and the adaptation to adverse environments. Pomegranate (Punica granatum L.)—a high-value fruit tree with ecological, economic, health, and ornamental importance—exhibits notable salt tolerance. While GRAS genes have been characterized in various species, their functional roles in pomegranate remain underexplored. In this study, 54 GRAS genes (PgGRAS) were identified in the pomegranate genome and were found to be unevenly distributed across eight chromosomes. Phylogenetic analysis grouped these genes into eight subfamilies, revealing highly similar conserved motifs, functional domains, and gene structures within each group. Notably, the DELLA subfamily is distinguished by a unique DELLA domain. Our findings indicate that the expansion of GRAS genes in pomegranate may be linked to fragment duplication events, and many PgGRAS genes contain both phytohormone- and stress-responsive cis-elements. Under 200 mM NaCl treatment, the expression of two DELLA genes was markedly upregulated. Therefore, PgGRAS24 was selected as a candidate gene for stable expression in Arabidopsis to further verify the role of DELLA family members in plant salt tolerance. Overall, this study provides new insights into the molecular functions of the GRAS gene family in pomegranate, gives insights into their role in salt stress tolerance, and lays a theoretical foundation for developing salt-tolerant pomegranate varieties.