The ever expanding role of aquaglyceroporins: confirmation of protein-facilitated boron transport

Abstract

The exact mechanism of transport of boron (B) entering the plant cell as boric acid B(OH)₃, has become hotly debated with evidence for both passive and protein facilitated transport. Here we put the controversy to rest by confirming that boron influx into plants can be partially controlled by opening and closing of channel-like transport proteins. Using treatments that were likely to inhibit membrane transporters capable of facilitating B transport, we confirmed that at least 50% of B transport could be contributed by a transporter of some type in barley roots. Based on the physiochemical similarities between B(OH)₃ and other solutes that were known to be transported via aquaglyceroporins, we hypothesised that aquaglyceroporins would be likely candidates to facilitate B(OH)₃ transport into the cytoplasm. We demonstrated using functional yeast complementation that two barley root aquaglyceroporins, HvPIP1;3 and HvPIP1;4, were both capable of facilitating B transport. This finding has demonstrated yet another function of aquaglyceroporins.