Figure 5.

4MeOI3M is transported in a PEN3-dependent manner. A, PEN3 overexpression enhances [³H]4MeOI3M export from protoplasts. Leaf mesophyll protoplasts isolated from Col-0 (WT), pen3-1, and 35S::PEN3 plants were loaded with [³H]4MeOI3M or [¹⁴C]IAA. Export of radioactively labeled compounds was measured by scintillation counting of supernatants. Data are plotted as export relative to initial export. B, PEN3-dependent uptake of [³H]4MeOI3M into microsomes. Microsomes isolated from Col-0 (WT), pen3-4, and 35S::PEN3 mixotrophic liquid cultures were incubated with [³H]4MeOI3M and [¹⁴C]IAA in the presence (clear bars) or absence of ATP (hatched bars). After 10 s and 2 min of incubation, samples were harvested, washed, and subjected to scintillation counting. Data are plotted as relative uptake normalized to the initial time point (10 s). C, unlabeled 4MeOI3M and 4MeOI3Cys compete with [³H]4MeOI3M microsomal uptake. Microsomes isolated from 35S::PEN3 mixotrophic liquid cultures were incubated with [³H]4MeOI3M in the presence of solvent or a 100-fold excess of unlabeled 3MeOI3M or 4MeOI3Cys. Samples and data handling were performed as in B. Combined data of at least four independent experiments with four replicates each are presented. Significance analyses were performed by unpaired t tests (*, p < 0.05). Error bars, S.E.