FIGURE 9.

Assaying activity of recombinant ZmEXPB6 proteins in vitro. Extension of frozen-thawed basal leaf sections (5-cm length/1.5-cm width) in response to a force applied to leaf sections treated with recombinant ZmEXPB6 (light gray) or heat-inactivated recombinant ZmEXPB6 protein (dark gray). Extension is in mm, as measured with a linear variable differential transducer until point of breakage of leaf sections, as plotted over time. Extension is in response to application of 0.2 μg of ZmEXPB6 protein per cm² ad- and abaxial leaf surface. Representative kinetics of equivalent recordings are from independent experiments (n = 14). Inset, comparability between leaf segments was achieved by using a segment left of the mid rib and the congruent segment right of the mid rib.