Brad M. Binder, PhD - US grants

The plant hormone ethylene regulates many critical processes in plants including growth, fruit ripening, senescence, and shedding of leaves and petals. The first step in this signaling pathway is the binding of ethylene to receptors. Plants contain multiple ethylene receptor isoforms. The first to be isolated and the most studied is the ETR1 receptor from the model plant, Arabidopsis thaliana. Despite over a decade of study, the mechanisms for how the ETR1 receptor works are still unknown. The focus of this research project is to follow up on the recent observation from the Binder laboratory that the ETR1 receptor has multiple and unique functions. Loss of the ETR1 receptor isoform, but not other isoforms, causes loss of ethylene-stimulated nutations (oscillatory bending) yet results in more sensitive responses to ethylene for other traits such as inhibition of growth. These apparently contradictory results represent the first description of a non-overlapping role for an ethylene receptor. Therefore the PI will study the role of the ETR1 receptor in a new context to uncover more details about ethylene receptor function and output. To do this, the output of the ETR1 receptor that leads to nutations versus other traits will be delineated. There are three general aims to this project. The first is to determine whether or not there are multiple signaling pathways downstream of ETR1. The second aim is to ascertain which domains or sites on ETR1 are required for nutations versus other characteristics. Both of these objectives will be addressed using physiological analysis of mutants. The third aim is to determine whether or not the paradoxical role of ETR1 is caused by changes in the distribution of ETR1 within the growing plant. These studies will provide details about how ethylene receptors function to regulate multiple traits. This multifaceted project will transform our understanding about links between events at the molecular level with those at the organ level to give a broader understanding of how plants grow and develop.

Broader Impacts of the Project:
This project will enhance research and educational infrastructure by broadening opportunities for undergraduate and graduate students to engage in research in the Binder lab. Dr. Binder also encourages high school students to engage in lab research. He participates in the University of Tennessee Pre-Collegiate Research Scholars Program that is a collaboration between The University of Tennessee and the Science Academy at Farragut High School in Knoxville. Currently one student is in the lab through this program and another was recruited from another high school independently. This project will enhance collaborations between the University of Tennessee and high schools in the area. This is an important element in educating future scientists. Student training will occur under the mentorship of Dr. Binder. In addition, Dr. Binder will continue to visit local classrooms to talk about biology research and will mentor for Planting Science (plantingscience.org), an on-line program that provides a learning and research resource in the plant sciences for K-16 students and teachers. All these activities will increase awareness about scientific research and ensure interested students become our future scientists. The increased understanding about ethylene signaling gained from this project will have profound impacts on a variety of crop related practices, most notably on post-harvest storage practices. This research will provide more focus so that specific responses to ethylene can be manipulated without compromising plant survival and vigor.

A Research Experience for Undergraduates (REU) Sites award has been made to the University of Tennessee Knoxville (UTK) that will provide research training for 10 students, for 10 weeks during the summers of 2012- 2014. This "Sensing and Signaling" program, supported by both the NSF Directorate for Biological Sciences and the Department of Defense ASSURE program, focuses on a variety of experimental approaches, including computational biology, structural biology, neurobiology, cell biology and genetics, to study the ways organisms sense environmental cues and adapt to their surroundings. Faculty from the Department of Biochemistry and Molecular and Cell Biology will serve as mentors. Students will engage in full-time lab research and will participate in a variety of seminars and workshops, including ethics and the responsible conduct of research, networking, professional communication skills, career opportunities in industry and academia, and the graduate school application process. Students are also provided tours of the nearby Oak Ridge National Lab, including the high-performance computing and neutron facilities. REU students have access to state-of-the-art resources housed in individual faculty mentor labs as well as core facilities for advanced imaging, DNA sequencing, bioanalytical methods, etc. Recruitment for the program involves circulating flyers by mail, establishing a web site, and digital advertising through a variety of distribution methods, and campus visits. Students are selected based on academic record, faculty recommendations, and potential for outstanding research using modern approaches in solving biological problems. REU participants are tracked to determine their continued interest in science, their academic and career paths, and the impacts of the summer research experience. Information about the program will be assessed in collaboration with local assessment experts at UTK, participation in the web-based SURE III nationwide survey sponsored by Howard Hughes Medical Institute, and the NSF REU common assessment tool. More information is available by visiting http://web.bio.utk.edu/bcmb/summer/reu.html, or by contacting the PI (Dr. Cynthia Peterson at cbpeters@utk.edu) or the co-PI (Dr. Brad Binder at bbinder@utk.edu).

A major challenge in biology is to understand how events at the biochemical level lead to changes at the organismal level. In cyanobacteria, light stimulates movement towards (positive phototaxis) and away from (negative phototaxis) light. This is an important survival mechanism in cyanobacteria. The cyanobacterium Synechocystis contains a protein (SynETR) that has characteristics of both photoreceptors (important for phototaxis) and ethylene receptors. In plants, ethylene receptors mediate many responses that impact plant survival, but it is unknown what these receptors do in cyanobacteria. Prior results have shown that ethylene regulates phototaxis in Synechocystis via the SynETR protein. However, no detectable biosynthesis of ethylene was found. It is known that sunlight can interact with dissolved organics to abiotically produce ethylene in the concentration range where physiological effects on phototaxis are seen. Thus, this project tests the hypothesis that Synechocystis uses ethylene as an external chemical cue to influence phototaxis behavior. The overall goal is to elucidate the mechanism by which ethylene affects SynETR function in Synechocystis to modulate phototaxis. A combination of biochemistry, chemistry, physiology, and molecular biology will be used to address this goal. This combination of approaches has yielded a great deal of information about the ethylene receptors in plants and provides a paradigm for determining the function of SynETR in Synechocystis. The multifaceted research will increase our understanding about links between ethylene binding events at the biochemical level with physiological changes that occur at the organismal level. This, in turn, will provide a broader understanding about how cyanobacteria respond to their environment and integrate environmental cues to modulate phototaxis.

The research will enhance research and educational infrastructure by broadening opportunities for high school, undergraduate and graduate students to engage in research. Since cyanobacteria contribute significantly to atmospheric oxygen levels and fix a large portion of carbon in the atmosphere, it is important to understand the effects of ethylene on these organisms because levels of ethylene in the atmosphere continue to rise as an air pollutant from industrial activities. Additionally, a better understanding about ethylene and its impact on cyanobacteria will help us determine how to maximize their use for bioenergy needs.

Ethylene is a simple gaseous hormone that has profound effects on the growth and development of plants. It is a central regulator of growth including the regulation of fruit ripening, yellowing of leaves, shedding of leaves and petals, and responses to various stresses and pathogens. Many of these responses adversely affect crop yield and postharvest storage of fruits and vegetables. Because of this, much research has focused on understanding the mechanisms underlying ethylene responses. The goal of this meeting is to bring together established scientists and early career scientists including graduate students and postdoctoral researchers, to discuss the mechanisms by which ethylene functions. The research that will be discussed at this meeting is highly relevant to the agriculture, economy, and food security of the United States.

The conference program covers ethylene signaling and biosynthesis across a range of scales from biochemical to organismal. This includes information on the structure-function of key ethylene signaling pathway components, spatial and temporal changes of these key components within the cell, and the output networks that control responses including impacts on other hormone systems. Information presented at this meeting will include experiments performed in the model organism Arabidopsis, as well as non-model crop plants, basal lineage plants, and microbes. This conference will provide an important opportunity for researchers to exchange the most recent research on the mechanisms by which ethylene affects plants.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.