摘要
Previous studies have shown that Arabidopsis equilibrative nucleoside transporters （AtENTs） possess transport activities when produced in yeast cells and are differentially expressed in Arabidopsis organs. Herein, we report further analysis on the nucleoside transport activities and transcriptional patterns of AtENT members. The recombinant proteins of AtENTs 3, 6, and 7, but not those of AtENTs 1, 2, 4, and 8, were found to transport thymidine with high affinity. Contrary to previ- ous suggestion that AtENT 1 may not transport uridine, this work showed that recombinant AtENT 1 was a pH-dependent and high-affinity transporter of uridine. When grown on MS plates, the AtENT3 knockout plants were more tolerant to the cytotoxic uridine analog 5-fluorouridine than wild-type plants and the knockout plants ofAtENT 1 or AtENT6. Con- sistent with this observation, the AtENT3 knockout line exhibited a significantly decreased ability to take up [^3H]uridine via the roots when compared with wild-type plants and the plants with mutated AtENT 1 or AtENT6. This indicates that AtENT3, but not AtENTs 1 and 6, is the main transporter for uridine uptake in Arabidopsis roots. The transcription of AtENTs 1, 3, 4, 6, 7, and 8 was regulated in a complex manner during leaf development and senescence. In contrast, the six AtENT members were coordinately induced during seed germination. This work provides new information on the transport properties of recombinant AtENT proteins and new clues for future studies of the in vivo transport activities and physiological functions of the different ENT proteins in Arabidopsis plants.
基金
This work was supported by grants from the National Natural Science Foundation of China （39770491）
the Chinese Academy of Sciences （KSCX2-SW-304）.
