Mutation of Aquaporin Gene PIP2;5 Postpones Pollen Hydration in Arabidopsis

In flowering plants with dry stigmas, pollen hydration involves water movement, which may be facilitated by aquaporins. To explore the possibility underlying this biological process, we identified and characterized a mutant with a T-DNA insertion in PIP2;5, which encodes an aquaporin with water channel activity in the PIP2 subfamily. We monitored the pollination process (pollen hydration, germination, and pollen tube growth) of wild type pollen on stigmas of the mutant and wild type. Pollen hydration was postponed on the stigmas of the mutant, compared with that on wild type stigmas. However, pollen tube germination and growth was unaffected in the mutant. The PIP2;5 protein was located in the cell plasma membrane and was preferentially expressed in the stigma. Based on our results, we concluded that PIP2;5 might play an important role in water movement during pollen hydration.