Fig. 5.

Test of water channel function of selected barley MIPs through expression in yeast and subsequent swelling assays of isolated spheroplasts. (A) Swelling kinetics of a representative batch of spheroplasts. Each curve is the average of 10–20 swelling kinetics, fitted with two-exponential equations. Control spheroplasts were isolated from yeast which had been transformed with the empty vector used for transformation (pYeDP60u, negative control) or with an Arabidopsis MIP (AtTIP1;2) known to show water channel activity (positive control). (B) Rate constants of water flow in spheroplasts. Results are averages ±SD (error bars) of the analysis of (n) kinetics as shown in (A): HvPIP2;5, (4); HvTIP1;1, (8); HvTIP2;3, (8), HvPIP2;2, (8); HvPIP2;7, (2, no error bar shown, values of 4.5 and 3.6 s⁻¹); HvPIP1;2, (3); HvTIP1;2 (4); negative control, (3); and positive control (4). Rate constants of swelling of barley-MIP expressing spheroplasts were significantly higher (P <0.001) than that of (negative) control spheroplasts containing the empty vector used for transformation.