Physicochemical characterization and expression profiling under abiotic stresses of the raffinose synthase gene family in <italic>Lagerstroemia indica</italic>

Raffinose synthase (RS) is a key enzyme involved in plant osmotic adjustment and stress responses. To explore the functions of RS genes in Lagerstroemia indica, we systematically identified the LiRS gene family and analyzed their characteristics using bioinformatics and transcriptome analyses, as well as their expression patterns under abiotic stresses. A total of 13 LiRS genes were identified, most of which encode acidic and hydrophilic proteins that are predominantly localized to the cytoplasm. Gene Ontology (GO) and KEGG enrichment analyses indicated significant enrichment in glycosyl transfer, oxidative stress, and galactose metabolism pathways. Transcriptome and qRT-PCR analyses revealed that the expression of LiRS genes exhibits significant tissue specificity and stress-responsive specificity. Under salt stress, LiRS13 was strongly induced in leaves, whereas LiRS9 expression in roots was genotype-dependent. Under cold stress, LiRS4 and LiRS6 were rapidly activated. Under drought stress, LiRS9 and LiRS13, as early core response genes, were significantly induced. Collectively, these findings highlight the critical roles of LiRS genes in stress responses and provide a theoretical basis for improving stress tolerance in L. indica.