Regulation of Abiotic Stress Responses in Plants by the Ubiquitin Pathway

University Of California-Davis, Davis CA

Investigators

Abstract

This project aims to understand how plants respond to a stressful environment in order to survive. While it is known that plants synthesize a novel chemical when exposed to conditions such as cold, drought and high salinity, what is not understood is how the plant "cleans house", that is, how the stress signal is removed so that the plant can begin normal growth once the stress is gone. Both genetic and biochemical approaches will be taken to determine exactly how these changes happen. This research will provide training of multiple UC-Davis undergraduates through research projects and support a graduate student and a post-doctoral scholar. These individuals will learn scientific methodology and how to present scientific data to colleagues and the greater community. They will learn analytical skills and improve their speaking and writing abilities. The graduate student will have the opportunity to interact with K-12 schools in neighboring communities with large Hispanic populations. The researcher will interact with representatives of the California seed/agricultural biotechnology industries through the Seed Institute at UC-Davis. The researcher has established a connection with a local Sacramento high school teacher and will continue this collaboration. The high school students will learn experimental design and data analysis, and participate in scientific discovery. Plants respond to environmentally stressful conditions by upregulating expression of genes that help them cope. One family of transcription factors required for stress responses are called ABRE BINDING PROTEINS (ABFs), and are regulated at the protein level. Under stress they are activated to promote transcription and at the same time their degradation is stopped and protein levels increase. How stress causes these two changes in ABFs and their relationship to biological function are not understood. ABF amino acids responsible for regulating constitutive ABF proteolysis under normal growth conditions and for stress-induced protein stabilization will be determined through in vitro and in vivo degradation assays. DNA sequences encoding ABF proteins will be changed so they translate ABF proteins with deletions and/or amino acid substitutions. ABF segments will also be fused with coding regions of marker enzymes and stability of the fusion determined in rapid and quantitative assays. Altered proteins will be expressed and purified from bacteria and stability measured in plant lysates. Sequences will be introduced into plants, multiple stable lines expressing these proteins produced and the in vivo protein stability measured. The role of phosphorylation status will be assessed by measuring the stability of proteins with substituted predicted or possible phosphorylation sites with either alanine, which cannot be modified, or with aspartate, which mimics modification. Transgenic plants expressing ABF proteins with differences in degradation rates will be assessed for their growth phenotypes under normal and stress conditions to determine if modulation of degradation provides greater stress resistance without compromising normal growth.