Divergent Roles of SOG Family Genes in Salt Tolerance: A Comparative Genomics Study Between Barley and Rice

Salt stress is one of the major abiotic stresses limiting the yield of agriculture production worldwide. Rice is an aquatic summer crop, while barley represents a drought winter crop. Both are classified as diploid sequenced crops within the Poaceae family, and are vital staples in the world. As a plant-specific transcriptional regulator, suppressor of gamma response (SOG) plays crucial roles in plant adaptation under abiotic stresses by repairing DNA damage pathway. However, little research has reported the function of SOGs in barley and rice. This study presents the first genome-wide identification and comparative analysis of the SOG gene family in barley and rice, two cereal crops with contrasting salt tolerance. A total of 97 HvSOGs and 74 OsSOGs were identified in the genome of barley and rice, which were divided into three subfamilies. There was significant variation between barley and rice in terms of gene structures, motif compositions, gene duplication, and cis-elements. Notably, rice may have suffered stronger purifying selection pressure than barley, whereas the proportion of SOGs with stress-related cis-elements was significantly higher in barley than in rice. The expression patterns of SOGs in barley and rice tissues under salt stress indicated that barley's stronger salt tolerance was largely due to an energy-saving strategy in shoots. Moreover, homologous gene similarity comparison with sea barleygrass suggested that gene loss and possible functional divergence during evolution may contribute to salt sensitivity in rice. Functional validation of a differentially expressed OsSOG17 gene confirmed its positive regulatory role in salt tolerance. Our findings uncover an energy-saving strategy as a potential mechanism underlying differential salt tolerance, and functionally link a SOG gene to salt stress responses in rice.