Arabidopsis pollen TIPs involved in pollen tube elongation.

Reproduction in flowering plants includes processes, like pollen germination and pollen tube elongation, where water and/ or solutes movements must be finely regulated. These regulations suggest the participation of aquaporins mediating water and solutes transport. AtTIP5;1 and AtTIP1;3 are the only aquaporins that are selectively and highly expressed in Arabidopsis thaliana mature pollen. In a heterologous system (Xenopus oocytes), both TIPs showed urea and water transport but neither glycerol nor boric acid (Soto, FEBS Lett. 2008, 582). We found that tip1;3 and tip5;1 homozygous mutant plants showed significantly reduced pollen tube length under nitrogen starvation. This data suggests that AtTIP1;3 and AtTIP5;1 are involved in nitrogen metabolism during pollen tube elongation. To understand the specific role of both TIPs, we generated transgenic plants that overexpress GFP-AtTIP5;1 and GFPAtTIP1; 3 fusion proteins studying their subcellular localization.