Which kind of plant do you want to analysis? I can give you an example of process of identification of transporter in sugarbeet. You will need to do combine protiomic analysis. At first select the vacular membrane and the tonoplast then electrophysiological analysis that will show you BvTST2.1 transporter that is responsible for vacular sucrose uptake in sugarbeet.

Dear Evans, the attached files may provide you detailed information.

probably when the root is growing transporters genes most expressed because root is heterotroph and when its growing, its needs sugar.

you can search NCBI and fiend gene locations for transporters and measurement their expressed.