Bundle-sheath aquaporins play a role in controlling Arabidopsis leaf hydraulic conductivity

The role of molecular mechanisms in the regulation of leaf hydraulics (Kleaf) is still not well understood. We hypothesized that aquaporins (AQPs) in the bundle sheath may regulate Kleaf. To examine this hypothesis, AQP genes were constitutively silenced using artificial microRNAs and recovery was achieved by targeting the expression of the tobacco AQP (NtAQP1) to bundle-sheath cells in the silenced plants. Constitutively silenced PIP1 plants exhibited decreased PIP1 transcript levels and decreased Kleaf. However, once the plants were recovered with NtAQP1, their Kleaf values were almost the same as those of WT plants. We also demonstrate the important role of ABA, acting via AQP, in that recovery and Kleaf regulation. These results support our previously raised hypothesis concerning the role of bundle-sheath AQPs in the regulation of leaf hydraulics.