DEREPRESSED SULFATE TRANSPORTERS ARE STRONGLY AND RAPIDLY REPRESSED AFTER SULFATE ADDITION TO SULFUR-DEPLETED VITIS CELLS.

A cell system of two Vitis species,Vitis vinifera cv. Touriga Nacional and Vitis rupestris, was chosen to study the response to sulfate deficiency and sulfate resupply through the analysis of sulfate influx and the expression of sulfate transporter transcripts. Cell suspensions were grown under two sulfate conditions: S sufficient (+S; 1.5 mM of MgSO4) and S deficient (-S). Both species were equally affected by the S-deficient conditions of the medium. After 24 h in -S medium, cells of both species showed a significant increase in sulfate influx rate, which was maintained throughout the culture cycle, reaching a maximum at days 4-5 in -S conditions. The relative expression of sulfate transporters from V. vinifera and V. rupestris, VvST and VrST, analyzed by real-time PCR, confirmed a strong derepression of the sulfate transporters in -S conditions. The enhanced influx rates and the upregulation of VvST and VrST were rapidly reversed by the addition of SO2-4 to the -S medium. Vitis vinifera showed a faster response at the protein level measured by the influx rates, while in V. rupestris, the effect was demonstrated primarily on the relative expression of VrST. [ABSTRACT FROM AUTHOR]