Abstract
Plants perceive moisture gradients by their roots and elongate them toward water sources to effectively obtain a limited amount of water in soil (hydrotropism). Little is known about the genes involved in hydrotropism of roots. We previously reported the reduced hydrotropic response of an Arabidopsis mutant defected in AKT2, which encodes a voltage-gated K+ channel. To gain a insight into the functional role of AKT2 in hydrotropism, we examined the spatial expression pattern of AKT2 during hydrotropic response using pAKT2::GUS transgenic plants. In the absence of a moisture gradient, AKT2 expression was uniformly observed in the phloem of roots. Under a moisture gradient, however, AKT2 expression was preferentially detected in the phloem of the outer (dry) side of bending roots rather than that of the inner (moistened) side. The results suggest that asymmetric accumulation of AKT2 in phloem plays a role in the hydrotropic response of roots.
