Genome-wide identification of the expansin gene family in Rosa rugosa and overexpression of RrEXPA1 contributes to drought and salt stress tolerance in Arabidopsis.
The expansin (EX) gene family plays a crucial role in the growth and development of various plants, as well as responses to biotic and abiotic stresses. However, genome-wide analysis of the EX gene family and their functions in drought and salt stress tolerance has not been examined in Rosa rugosa. In this study, a total of 30 RrEX genes were identified and located on seven different chromosomes. Phylogenetic analysis classified these genes into four subfamilies: EXPA (24 members), EXPB (3 members), EXLA (1 member), and EXLB (2 members). The average amino acid length was 269.17 aa, with isoelectric points ranging from 4.79 to 9.97. Most members exhibited high aliphatic indices and protein stability, suggesting their adaptability to diverse environments. The synteny analysis provided insights into the evolution of the EX gene family in rose. Toxicity and autoactivation assays confirmed that BD-RrEXPA1 was non-toxic to yeast cells and lacked autoactivation activity, indicating its suitability for yeast two-hybrid screening. The transgenic Arabidopsis lines overexpressing RrEXPA1 improved seed germination and root length under abiotic stress. In addition, the overexpression lines showed reduced malondialdehyde (MDA) levels and increased chlorophyll content and superoxide dismutase (SOD) activity. These results suggest that RrEXPA1 may enhance stress tolerance by promoting root elongation and modulating physiological responses. This study provides important insights into the role of RrEXs in salt and drought stress and lays the foundation for further studies on the regulatory mechanisms of abiotic stress.