Role of the Unfolded Protein Response in Environmental Stress Tolerance in Maize

Iowa State University, Ames IA

Investigators

Abstract

This research will investigate strategies for protecting maize, the major U.S. food, feed and fuel crop, from environmental stress. Maize can perceive and respond to adverse environmental conditions through a process called the unfolded protein response (UPR). Folding is a critical, but delicate step in the biosynthesis of proteins, and it can be easily upset by adverse conditions, such as high temperature. When this happens, misfolded proteins accumulate and activate a cascade of stress response genes. One of the objects of this project is to characterize in depth the cascade of genes to better understand how they protect maize from stress. Investigations in other plants has revealed that stress conditions eliciting the UPR also activate a process called autophagy in which plant cells repair stress damage. Therefore, another aim of this project is to discover how stress signals activate the autophagy machinery. In response to stress, other plants slow down protein synthesis to prevent overburdening the process of protein folding. In this project an investigation will be conducted to determine whether maize does this by degrading some of the messenger RNAs encoding proteins. Finally, attempts will be made to modify the UPR and probe more deeply into its operation by using new gene editing techniques. In parallel, there will be a focus on links between learning and research at the undergraduate level. This will be done through the development of easily accessible training on line and peer-support learning communities. In this project, it is expected that new gene targets involved in ER stress responses in maize will be revealed through extensive transcriptomic analysis. It is anticipated that those targets may provide a clearer picture of both cell survival activities and cell death mechanisms in response to stress. In addition, these analyses will aid in uncovering the signaling pathways by which stress elicits the proliferation of the ER and activation of autophagy. While some UPR responses involve the upregulation of stress response genes, other responses result from the degradation of specific RNA transcripts brought about by Regulated IRE1-Dependent RNA Degradation (RIDD)and microRNA action. In this regard, the degradome as well as the transcriptome will be used to determine the role of selective RNA transcript degradation in maize stress responses. This research project is also expected to reveal through 'translateome' analysis whether ER stress is also mitigated in maize by selective and/or global regulation of the translation of RNA transcripts. A compelling reason for the selection of maize as a model for these studies is that the UPR has already been demonstrated in maize in the field. Therefore, variation in stress response in different lines of maize will be studied both in the laboratory and in the field with the goal of identifying genetic determinants that condition the UPR.