Figure 4: NPF3 is a GA transporter in Xenopus laevis oocytes.

(a) Uptake of GA₃-Fl and fluorescein by NPF3, NPF2.11 (GTR2) and non-injected oocytes. Oocytes were incubated for 30 min in 100 μM GA₃-Fl (pH5). Picture shows a representative oocyte from 3 oocytes. (b) Uptake of GA₃ by NPF3, NPF2.11 (GTR2) and non-injected oocytes at pH5 and pH7. Oocytes were incubated for 1 h in 100 μM GA₃ (pH5 or pH7) (n=3). N: below detection limit. (c) Bioactive GA₁, GA₃ and GA₄ uptake at pH 5.5 and pH 7.5 by NPF3. NPF3-expressing or non-injected oocytes were incubated for 1 h in 100 μM with the indicated GAs (n=3). N: below detection limit. (d) Confocal images of WT root elongation zone immersed in GA₃-Fl (5 μM, 3 h) in indicated pHs. Right graph: quantification of GA₃-Fl fluorescence intensity. Presented are averages±s.e. roots per genotype and 26 sampling points per root (n=104). Bar, 50 μm. (e) Uptake of GA₃-Fl and GA₄-FI by oocytes expressing the indicated endodermis expressed NPFs (n=4). (f) Uptake of GA₃ and GA₄ by oocytes expressing the indicated endodermis expressed NPFs (n=4). (g) Competition of GA₄ uptake mediated by NPF3 and NPF4.1 (AIT3) expressing oocytes. Oocytes expressing either NPF3 or NPF4.1 were exposed to 300 μM GA₄ alone or 300 μM GA₄ together with either 5 mM NO₃⁻, 5 mM dipeptide (Gly-Leu), 5 mM histidine (His) or 5 mM JA-isoleucine (JA-Ile; n=5). (h) Uptake of indicated GA precursors and catabolite mediated by NPF3 and NPF4.1 (AIT3) expressing and non-injected oocytes. Oocytes were incubated for 1 h in 100 μM of the indicated GA (at pH5) (n=5). (i) Uptake of GA₄ by Oryza sativa and Medicago truncatula NPF3.1 orthologs as defined by ref. 26. Oocytes expressing A. thaliana NPF3 (AtNPF3.1), O. sativa NPF3.1 (OsNPF3.1) or M. truncatula NPF3.1 (MtNPF3.1) or non-injected oocytes were incubated for 1 h in 300 μM GA₄ at pH5 (n=5). In all graphs: Error bars are s.d. unless indicated otherwise. Groups are determined by one-way analysis of variance and (P<0.05). non-inj., non-injected.