Genome-wide identification and evolutionary analysis of SUT genes reveals key regulators of drought stress response in finger millet (Eleusine coracana)

Abstract

Sucrose transporters (SUTs) mediate sucrose movement across plant membranes, playing a crucial role in carbon allocation and stress responses. Although finger millet (Eleusine coracana) is known for its inherent drought resistance, the specific involvement of SUT genes in this characteristic is still unclear. This study aimed to identify the SUT genes of millet and to assess their expression in drought conditions. Five SUT genes (EcSUT1-EcSUT5) were identified that encode proteins with 9–12 transmembrane domains. Phylogenetic analysis clustered these SUT members across all three main SUT groups, suggesting an evolutionary divergence within the family. Synteny analysis revealed conserved genomic regions, with EcSUT2 showing 91–94% identity with orthologs in closely related grasses. Structural models further confirmed their typical transmembrane architecture. Interaction analysis identified EcSUT2 as a key interaction with SWEET transporters. Furthermore, the promoter regions of EcSUT2 and EcSUT5 were found to be enriched with hormone and stress-responsive elements. Under drought conditions, EcSUT1-EcSUT4 displayed transient induction, while EcSUT5 showed sustained upregulation, especially in the roots, notably after 48 h. The finger millet SUT family exhibits evolutionary conservation within grasses, with individual genes that play different roles in stress response. The persistent upregulation of EcSUT5 under drought strongly suggests its involvement in maintaining sucrose transport during long-term adverse conditions. This candidate gene requires further functional validation to uncover the stress dynamics for sustainable crop improvement.