Molecular Dissection of Autophagy in Maize and its Roles in Nutrient Recycling and Stress Protection

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

PI: Richard D. Vierstra (University of Wisconsin - Madison) CoPI: Marisa S. Otegui (University of Wisconsin - Madison) Plants employ sophisticated mechanisms to traffic and recycle intracellular constituents needed for growth and development, housekeeping, and survival under nutrient stress. One involves the sequestration of cytoplasmic material in autophagic vesicles and subsequent delivery of these vesicles to the vacuole for breakdown or storage. Prior work made substantial progress toward defining the mechanisms underpinning autophagy through molecular, genetic, and imaging analyses of a set of essential autophagy-related (ATG) components in both Arabidopsis and maize. Of relevance to agriculture were recent findings that autophagy is critical to nitrogen-use efficiency in maize and the discovery of a novel autophagic route that operates in maize seeds. The objectives of this project are to: (i) further define the maize ATG system at the biochemical and genetic levels; (ii) provide an integrated view of how autophagy impacts maize growth, development, and yield during nitrogen stress by combining atg mutants with phenotypic, cell biological, proteomic, metabolomic, and transcriptomic analyses; (iii) identify the cargo degraded by autophagy via proteomic characterizations of autophagic vesicles; and (iv) define the molecular mechanism underpinning ATG-independent autophagy during maize seed protein accumulation. Collectively, this research will provide the first systems view of autophagy in a crop plant and its role in nitrogen-use efficiency. More broadly, this research will also generate important reagents, techniques, mutants, transgenic lines, germplasm, and cargo catalogs that will provide a much needed foundation to appreciate autophagy in the important crop, maize. With such knowledge, it should be possible to re-engineer crops that more efficiently use nitrogen and other nutrients, that better remobilize these nutrients to areas of new growth and storage, that display improved leaf senescence and fruit ripening characteristics, and that provide better grain yields. As a broader impact, this project is designed to provide an interdisciplinary vehicle for training the next generation of plant scientists using state-of-the-art genetic, proteomic, transcriptomic, metabolomic, and cell biological approaches to study crop physiology. Participants include research scientists, graduate students, and several undergraduates at Wisconsin or attending the UW-summer REU experience hosted by the Integrated Biological Sciences Summer Research Program, as well as high school students sponsored by the Wisconsin Youth Apprenticeship Program (YAP) in Biotechnology. YAP-Biotechnology is designed to expand the workforce in biological sciences by providing practical training to high school juniors and seniors through formal technology classes combined with real-life research experiences. Additional educational impacts involve cell biology workshops developed by the CoPI, who serves as the supervisor of the NSF-sponsored Plant Imaging Center, related to the next generation tomographic imaging techniques that will be refined during this project. Some of these refinements will be developed through an Introduction to Engineering Design course project organized by the UW-School of Engineering that will create devices optimized for imaging maize endosperms. Free and unencumbered public access to the RNA-seq, metabolomic, and proteomic datasets generated by this project will be facilitated by deposition of the data at MaizeGDB (http://www.maizegdb.org/) and the NCBI Gene Expression Omnibus (GEO; http://www.ncbi.nlm.nih.gov/geo/) public repositories. Mutant germplasm and stable transgenic lines will be made available through the Maize Genetics Cooperative Stock Center (http://maizecoop.cropsci.uiuc.edu).