Abstract
Cytokinins (CKs) are mainly transported through vasculatures in the form of nucleosides. Growth analysis of budding yeast (Saccharomyces cerevisiae) cells expressing OsENT2, an equilibrative nucleoside transporter of rice, showed that OsENT2 mediated uptake of isopentenyladenine riboside (iPR, Km= 32 uM) and trans-zeatin riboside (Km= 660 uM), suggesting that OsENT2 participates in iPR transport in planta (Plant Physiol., 2005, 138, 196-206). The OsENT2 promoter drove the expression of the ss-glucuronidase reporter gene in the scutellum during germination and in vascular tissues in germinated plants, suggesting a participation of OsENT2 in the retrieval of endosperm-derived nucleosides by the germinating embryo and in the long-distance transport of nucleosides in growing plants, respectively. Further functional analysis of OsENT2 is currently being undertaken by using Tos17 tagged lines and RNAi knock down mutants.
