ABCG11 modulates cytokinin responses in .

The Arabidopsis ABC transporter ABCG11 transports lipidic precursors of surface coating polymers at the plasma membrane of epidermal cells. Mutants in exhibit severe developmental defects, suggesting that ABCG11 might also participate in phytohormone-mediated development. Here, we report that ABCG11 is involved in cytokinin-mediated development. The roots of mutant seedlings failed to respond to cytokinins and accumulated more cytokinins than wild-type roots. When grown under short-day conditions, exhibited longer roots and shorter hypocotyls compared to wild type, similar to , a knockout mutant in a cytokinin transporter. Treatment with exogenous -zeatin, which inhibits primary root elongation in the wild type, enhanced primary root elongation. It also increased the expression of cytokinin-responsive Arabidopsis response regulator () genes, and the signal of the :: reporter in roots compared to wild-type roots, suggesting that cytokinin signaling was enhanced in roots. When we treated only the roots of with -zeatin, their shoots showed lower induction than the wild type. The double mutant did not have additional root phenotypes compared to . Together, these results suggest that ABCG11 is necessary for normal cytokinin-mediated root development, likely because it contributes to cytokinin transport, either directly or indirectly.