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

The role of molecular mechanisms in the regulation of leaf hydraulics (K-leaf) is still not well understood. We hypothesized that aquaporins (AQPs) in the bundle sheath may regulate K-leaf. 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 K-leaf. However, once the plants were recovered with NtAQP1, their K-leaf 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 K-leaf regulation. These results support our previously raised hypothesis concerning the role of bundle-sheath AQPs in the regulation of leaf hydraulics.