IdenticationofRegionsinthe.PDF

Identification of Regions in the Receiver Domain of the ETHYLENE RESPONSE1 Ethylene Receptor of Arabidopsis Important for Functional Divergence1[OPEN] 2 2 3 Arkadipta Bakshi , Rebecca L. Wilson , Randy F. Lacey, Heejung Kim , Sai Keerthana Wuppalapati, and Brad M. Binder* Genome Science and Technology Program (A.B., B.M.B.) and Department of Biochemistry, Cellular, and Molecular Biology (R.L.W., R.F.L., H.K., S.K.W., B.M.B.), University of Tennessee, Knoxville, Tennessee 37996 ORCID IDs: 0000-0002-3309-8185 (R.L.W.); 0000-0002-8172-2034 (B.M.B.). Ethylene influences the growth and development of Arabidopsis (Arabidopsis thaliana) via five receptor isoforms. However, the ETHYLENE RESPONSE1 (ETR1) ethylene receptor has unique, and sometimes contrasting, roles from the other receptor isoforms. Prior research indicates that the receiver domain of ETR1 is important for some of these noncanonical roles. We determined that the ETR1 receiver domain is not needed for ETR1’s predominant role in mediating responses to the ethylene antagonist, silver. To understand the structure-function relationship underlying the unique roles of the ETR1 receiver domain in the control of specific traits, we performed alanine-scanning mutagenesis. We chose amino acids that are poorly conserved and are in regions predicted to have altered tertiary structure compared with the receiver domains of the other two receptors that contain a receiver domain, ETR2 and ETHYLENE INSENSITIVE4. The effects of these mutants on various phenotypes were examined in transgenic, receptor-deficient Arabidopsis plants. Some traits, such as growth in air and growth recovery after the removal of ethylene, were unaffected by these mutations. By contrast, three mutations on one surface of the receiver domain rendered t