Brad Binder
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Research Statement
I am interested in understanding the control of growth and development in plants. Because plants are sessile, one of the main ways they respond to alterations in their environment is through altered growth. These alterations in growth are mediated by a variety of phytohormones; most of my work is on the phytohormone ethylene. Ethylene is a gas produced by plants that regulates and influences many critical physiological and developmental processes in plants making it of agricultural, horticultural and economic importance to understand its mode of action and to more fully understand how it affects plants. My research focuses on several aspects of ethylene biology.
One topic of interest is to further define the structure-function relationships of the receptors and the effects of transition metals on receptor function. The ethylene receptors were the first hormone receptors identified in plants. They form a multigene family, have homology to bacterial two-component receptors, and are thought to form homodimers. Interestingly, ethylene receptors are metalloproteins containing copper ions. While copper is the natural co-factor, we have shown that the other group 11 transition metals (silver and gold) support ethylene binding to the receptors while other metals do not. This observation is of interest because silver blocks ethylene action in the plant. These observations support the idea that silver may block conformational changes in the receptor because it is larger than copper. Future work in the lab will address this model. We are also interested in how the helixes of the receptor dimer interact to form the ethylene/copper binding pocket and how the ethylene binding event is transduced by the receptors.
A second area is to uncover new details about the ethylene signal transduction pathway downstream of the receptors. A major effort recently has been to use a computer-driven, time-lapse image acquisition system to study the kinetics of growth changes in etiolated seedlings of Arabidopsis thaliana. This system has revealed transient and subtle changes due to ethylene that would have otherwise remained unknown. Combining this approach with genetics and molecular biology has refined our understanding about ethylene receptor function and down-stream signal transduction components and has provided links between events at the molecular level with those at the organ level. In particular, there appear to be two phases to the ethylene response which can be genetically and pharmacologically distinguished. The second, slower phase response to ethylene is dependent on the EIN3 and EIL1 transcription factors. In contrast, the events leading to the first phase response remains unknown. Efforts continue to define the central roles for EIN3 and EIL1 and to uncover more details about the control of the first phase response.
A third area of current research is based on the recent observation that ethylene stimulates nutational bending of hypocotyls that are dependent on the ETR1 receptor. Nutations (also called circumnutations) are nodding or coiling movements and are thought to be important in allowing the roots and shoots to penetrate the soil. Thus, they are likely to be important in seedling survival. Loss-of-function mutants of the ETR1 receptor results in loss of the nutation phenotype while loss-of-function mutant combinations of the other receptor isoforms results in constitutive nutations in air. The basis for this unique role is now being investigated. The observation that ETR1 has a unique role in ethylene-stimulated nutations suggests that the other receptor isoforms might have unique roles in developmental and physiological processes such as senescence, abscission and responses to abiotic stresses. This idea is currently being tested. We have also found that auxin transport is involved in ethylene-stimulated nutations. This provides a good system to explore the links between ethylene signaling and auxin transport.
By combining biochemistry, molecular biology, genetics, and physiology, we are gaining a better understanding of ethylene signal transduction and the complexity of interactions between ethylene and other signaling systems in the plant.
Selected Publications
Gao Z, Wen C-K, Binder BM, Chang J, Chiang Y-H, Kerris III RJ, Chang C, Schaller GE. (2008). Heteromeric Interactions Among Ethylene Receptors of Arabidopsis. Journal of Biological Chemistry (In press)
Pirrung MC, Bleecker AB, Inoue Y, Rodriguez FI, Sugawara N, Wada T, Zou Y, Binder BM. (2008) Ethylene Receptor Antagonists: Strained Alkenes Are Necessary But Not Sufficient. Chemistry and Biology 15: 313-321. [Abstract]
Binder BM, Rodriguez FI, Bleecker AB, Patterson SE. (2007) The Effects of Group 11 Transition Metals, Including Gold, on Ethylene Binding to the ETR1 Receptor and Growth of Arabidopsis thaliana. FEBS Letters 581: 5105-5109. [Abstract]
Binder BM, Walker JM, Gagne JM, Emborg TJ, Hemmann G, Bleecker AB, Vierstra RD. (2007) The Arabidopsis EIN3-Binding F-Box Proteins, EBF1 and 2 Have Distinct but Overlapping Roles in Regulating Ethylene Signaling. The Plant Cell 19: 509-523. [Abstract]
Wang W, Esch JE, Shiu S-H, Agula H., Binder BM, Chang C, Patterson SE, Bleecker AB. (2006) Identification of Important Regions for Ethylene Binding and Signaling in the Transmembrane Domain of the ETR1 Ethylene Receptor of Arabidopsis The Plant Cell 18: 3429-03442. [Article]
Binder BM, O’Malley RC, Wang W, Zutz TC, Bleecker AB. (2006) Ethylene Stimulates Nutations that are Dependent on the ETR1 Receptor. Plant Physiology 142: 1690-1700. [Article]
O'Malley RC, Rodriguez FI, Esch JJ, Binder BM, O'Donnell P, Klee HJ, Bleecker AB. (2005) Ethylene-binding activity, gene expression levels, and receptor system output for ethylene receptor family members from Arabidopsis and tomato. The Plant Journal. 41: 651-659. [Abstract]
Binder BM, O'Malley RC, Moore JM, Parks BM, Spalding EP, Bleecker AB. (2004) Seedling Growth Response and Recovery to Ethylene: A Kinetic Analysis. Plant Physiology 136: 2913-2920. [Abstract ] (Included cover image for ethylene special issue)
Binder BM, Mortimore LA, Stepanova AN, Ecker JR, Bleecker AB. (2004) Short Term Growth Responses to Ethylene in Arabidopsis Seedlings Are EIN3/EIL1 Independent. Plant Physiology 136: 2921-2927. [Abstract] (Included cover image for ethylene special issue)
Rodriguez F, Esch J, Hall A, Binder B, Schaller GE, Bleecker AB. (1999) A Copper Cofactor for the ETR1 Receptor from Arabidopsis. Science 283: 996-998. [Abstract]
Contact Information
Office:
Room 343
Hesler Biology Building
Phone: (865) 974-7994
Lab:
Room 316
Helser Biology Building
Phone: (865) 974-7997
Email: bbinder@utk.edu