Abstract
The plasma membrane intrinsic protein (PIP) forms the pore for water transport as a water channel in plant cells. We have studied the molecular mechanism of water transport in roots of barley (Hordeum Vulgare cv. Haruna-nijo). Quantitative RT-PCR analyses using roots of barley plants revealed significant reductions in the accumulation of 6 out of 10 HvPIP mRNA in response to 200 mM NaCl. Characterization of water permeability of barely roots using a pressure chamber showed that water permeability was extremely down-regulated in 200 mM NaCl condition. Furthermore, phosphorylation was found to regulate water transport activity. HvPIP1 proteins did not show apparent water transport activity when they were expressed alone in Xenopus laevis oocytes. However, co-expression of HvPIP1 proteins with HvPIP2 proteins was shown to enhance water transport activity of HvPIP2 proteins. The regulation mechanism of water transport via HvPIP proteins in barley roots under salinity stress will be discussed.
