A Small GTP-Binding Gene ScRan from Sugarcane is Involved in Responses to Various Hormone Stresses and Sporisirium scitamineum Challenge

The ras-like nuclear GTP-binding protein (Ran) is known as a molecular switch and plays an important role in eukaryotic metabolism. In this study, a differentially expressed EST sequence from our previous suppression subtractive hybridization libraries of sugarcane under Sporisirium scitamineum infection was used as the probe, and an 836-bp-long sugarcane Ran gene (ScRan) was cloned from sugarcane smut-resistant genotype YC05-179. Bioinformatic analysis revealed that the ScRan gene contained a 666-bp-long complete open-reading frame, encoding a stable 25-kDa acidic protein with four core domains GDGGTGKT (I), DTAG (II), NKVD (III), and EISAK (IV), and without the signal peptide. The inducing expression results of ScRan in Escherichia coli showed that the molecular weight of ScRan was about 20–35 kDa. Sequence alignment and phylogenetic analysis indicated that ScRan protein was conservative in evolution. ScRan protein was located in both the nucleus and the cytoplasm and could interact with sugarcane Sc14-3-3 protein (GenBank Acc. No.: AY222859). qRT-PCR analysis demonstrated that the expression of ScRan was higher in root than all the other sugarcane tissues including bud, leaf sheath, stem pith, and epidermis. The upregulation of ScRan in case of abscisic acid (ABA), salicylic acid (SA), and methyl jasmonic acid (MeJA) stimuli indicated its positive involvement in sugarcane responses to phytohormone ABA, SA, and MeJA signaling. ScRan was positively responded to S. scitamineum infection in the early stage but was inhibited in the later stage. These results would facilitate understanding the important role of the ScRan gene in sugarcane defense against various hormone stresses and S. scitamineum stress.