Figure 8.

Rescue of growth, nutations, and growth recovery by chimeric receptor transgenes. The triple etr1-6 etr2-3 ein4-4 were transformed with chimeric cDNA constructs with domains swapped between ETR1 and EIN4 as labeled. All transgenes were under the promoter control of ETR1. For comparison, data from Col (wt), etr2-3 ein4-4 double mutants, and etr1-6 etr2-3 ein4-4 triple mutants are included. A, The growth rates in air of triple mutants transformed with the indicated chimeric receptor are plotted. Growth rate in air was determined from the first hour of growth kinetic measurements prior to the introduction of ethylene. Data represents the average growth rate ± sem. B, Nutations in response to 1 μL L⁻¹ ethylene were measured in etr1-6 etr2-3 ein4-4 triple mutants transformed with the indicated ETR1-EIN4 chimeric receptor. Nutation amplitudes were measured as described in the “Materials and Methods.” The average peak nutation amplitude ± sem is plotted. C to E, Growth kinetic profiles for triple mutants transformed with chimeric receptors are shown. Seedlings were allowed to grow for 1 h in air, followed by the addition of 1 μL L⁻¹ ethylene (down arrow). Two hours later ethylene was removed (up arrow) and seedlings grown in air for an additional 5 h. Growth rate was normalized to growth rate in the air pretreatment and represents the average ± sd for at least four seedlings in three separate experiments. Lines were fitted by hand. For comparison, each section shows the growth kinetic profile for wt (dashed black line), etr2-3 ein4-4 double mutants (dashed gray line), and etr1-6 etr2-3 ein4-4 triple mutants (dotted black line) taken from Figure 3C. In A and B data were analyzed with t tests and increases over the etr1-6 etr2-3 ein4-4 triple mutants were considered statistically significant for P < 0.001 (*) or P < 0.02 (#).