Role of the Two-Component Pathway in Mediating Ethylene Signal Transduction

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The plant hormone ethylene plays important and wide-ranging roles throughout plant growth and development, including regulation of seed germination, seedling growth, leaf and petal abscission, fruit ripening, organ senescence, and pathogen responses. How a single hormone mediates such a diverse array of processes and how these processes are integrated with other signaling pathways remain fundamental questions in plant biology. This project will explore a gene expression mechanism by which ethylene regulates such processes, thereby providing novel insights into ethylene signaling and regulation as well as avenues by which to modify ethylene responses in agriculturally important plants. A summer art-and-science course titled "Secrets of the Green World" will be developed in conjunction with this project, where students will employ scientific tools, engage in scientific thought, and be involved in a creative process that integrates science with art.The established pathway for ethylene signal transduction culminates in transcriptional regulation by the EIN3 family of transcription factors (TFs). Evidence indicates that the ethylene receptors may also signal through a two-component pathway, employing the type-B ARR family of TFs, to control a subset of the ethylene responses. This project presents an integrated set of experiments to determine how the type-B ARRs function in concert with the EIN3 family of TFs, building toward a systems level understanding of the ethylene transcriptional response. The first objective of this project is to characterize the role of physical interaction between type-B ARRs and EIN3 in transcriptional regulation. Mechanistic studies will be pursued to elucidate the basis for the interaction and how this interaction affects ethylene-dependent gene regulation. The second objective is to determine the suite of genes co-regulated by type-B ARRs and EIN3. ChIP-Seq and RNA-Seq based approaches will be used to identify the co-regulated targets, and systems-based approaches used to predict physiological roles for testing. The third objective is to characterize transcriptional cross-talk between the ethylene and cytokinin signaling pathways, since employment of two-component signaling elements by the ethylene pathway is predicted to affect signaling through the cytokinin pathway. Models for how TF cooperativity and sequestration regulate cross-talk between these phytohormone signaling pathways will be tested using transcriptomic and genetic approaches.