Fig. 4.

ABCG37 transports IBA and other auxinic compounds. (A) The absence of both ABCG36 and ABCG37 leads to increased [³H]IBA accumulation (P < 0.05 by ANOVA) in root tips, but does not affect [³H]IAA accumulation. (B) abcg37 (pis1-1) leaf mesophyll protoplasts show significantly lower export of [³H]IBA as compared with the wild-type protoplasts (P < 0.05 by ANOVA). (C) Expression of ABCG37 in S. cerevisiae leads to ABCG37 accumulation in the endoplasmic reticulum and increased retention of [³H]2,4-D and [³H]IBA (significantly different from the vector control, Student's t test, P < 0.05). (D) Expression of ABCG37 in S. pombe cells results in a decreased [³H]IBA accumulation, significant after 6 min (P < 0.05 by ANOVA). [³H]IBA concentration was 250 μM. (E) ABCG37 expression in HeLa cells confers active export of [³H]2,4-D and [³H]IBA compared with the empty vector (P < 0.05 by ANOVA). (F) When expressed in HeLa cells, PIN2, PIN7, ABCB1, and ABCB19 show a clear [³H]IAA transport (P < 0.005 by ANOVA), no significant [³H]IBA transport or IBA competition with [³H]IAA transport was observed. Auxin concentrations were 60 nM [³H]IAA, 60 nM [³H]IBA, and 180 nM unlabeled IBA (3× IBA). Values shown are means from three replicate experiments.