Abstract
The plasma membrane intrinsic protein (PIP), which belongs to the aquaporin gene family, functions as water channel in plant cells. We have newly isolated 6 full length PIP cDNAs from barley (Hordeum Vulgare). Quantitative RT-PCR analyses using roots of barley plants indicated that 6 out of 10 HvPIP genes were down-regulated in response to 200 mM NaCl stress. Water transport activity of HvPIP proteins was analyzed using Xenopus laevis oocytes. Unlike the case of HvPIP2 proteins, HvPIP1 proteins did not show apparent water permeability when they were solely expressed. Interestingly, however, HvPIP1;2 and 1;3 proteins showed significant water permeability when they were co-expressed with some specific HvPIP2 proteins in Xenopus oocytes. These results strongly suggest that HvPIP1 proteins play an essential role in water transport in vivo of barley plants as well as HvPIP2 proteins, forming heteromers with HvPIP2 proteins.
