A Novel Hexose Transporter in Rice Putatively Regulates the Uptake of Melatonin, the Potent Abiotic Stress Regulator

The present manuscript represents the identification and predictive structural characterization of novel human GLUT1-orthologue, melatonin transporter (MelT) in plants (especially rice) and its functional ability to transport melatonin. It is reported that melatonin binds to the same residues within GLUT1 as glucose. Homology modelling and docking analyses predicted overall sequence homology of melatonin transporter from rice (OsMelT) with GLUT1. The protein was predicted to contain 12 transmembrane helices and a PF00083.24 sugar transport domain (responsible for melatonin binding and release). The C-terminus was more structured, compared to the N-terminus, and phosphorylation sites were detected throughout the protein. The upstream analysis of MelT in rice showed the presence of cis acting motifs associated with abscisic acid and melatonin regulation, and induction to both abiotic and biotic stress. Expression studies validated the up regulation of OsMelT in presence of glucose and higher concentrations of exogenous melatonin. Overall, the study predicted the functional ability of OsMelT to transport melatonin and maintain the uptake and mobilization of the biomolecule at higher concentration.