Abstract:In this study, to learn the structure and function of the sucrose transporter gene (SUT1) of sweet sorghum, we first obtained the full-length cDNA of SUT1 by using homology-based cloning together with RACE technology. The cDNA sequence was then analyzed by using a variety of bioinformatics databases and software. The full-length cDNA of SUT1 contained 2472 base pairs, with a coding region of 1560 base pairs. This sequence encoded a protein of 519 amino acids in length with a molecular weight of 55kDa and a theoretical isoelectric point (pI) of 8.86. SUT1 was found to encode a hydrophobic membrane protein for which there was no signal peptide and corresponding cleavage site in its sequence. The SUT1 protein‘s topology featured 12 distinct transmembrane helices, 12 conserved domains, six serine phosphorylation sites, four threonine phosphorylation sites, two tyrosine phosphorylation sites, and a low complexity region. At the subcellular level, the SUT1 protein was mainly localized to the chloroplast thylakoid membrane, plasma membrane, Golgi body, and the membrane of endoplasmic reticulum. The secondary structure of SUT1 was mainly composed of alpha helix, consisting of 43.35% helix,34.68% random coil, 19.08% extended strand, and 2.89% beta turn. The SUT1 protein seemed to mainly play a role in the processes of transport and binding. The analysis of SUT1 gene expression indicated that it was expressed at varying levels in different tissues. The highest expression levels were found in the leaves, followed by the sheath, stem, and root, respectively, with the lowest expression in the tassel. By cloning the SUT1 gene and preliminarily predicting its structure, nature and functions, we have acquired valuable information which can be used to study the biological function of the SUT1 gene with respect to the relationship between source and sink in sweet sorghum.