Abstract
Auxin influx and efflux carriers are involved in auxin transport and plant development. Here we show that the mutant of rice (Oryza sativa L. ssp. indica cv IR8) arm2 is defective in the uptake of naturally-occurring auxin indole-3-butyric acid (IBA). The acropetal and basipetal transports of IBA are reduced in arm2 roots compared with wild type. In contrast, arm2 roots are normal with respect to uptake and transport of other natural auxin indole-3-acetic acid (IAA). Furthermore, arm2 roots are resistant to IBA but respond normally to IAA. Although the number of lateral roots in arm2 is slightly less compared to wild type, it increased to the level of wild type roots in the presence of 0.1 μM IBA. These results are consistent with the idea that ARM2 is involved in IBA uptake and suggest the presence of influx carrier system for IBA in rice roots.
