Role of Plant Transcriptional Adaptors in Cold-Regulated Gene Expression

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9728462 Thomashow Many plants increase in freezing tolerance in response to low nonfreezing temperatures, a phenomenon known as cold acclimation. Recent evidence indicates that cold acclimation involves the induction of cold-regulated genes. A primary research objective is to determine how plants sense low temperature and process the "cold signal" to induce the expression of freezing tolerance genes. Toward this end, an Arabidopsis cDNA has been isolated that encodes a transcriptional activator that binds to the CRT/DRE sequence, a cold- and drought-responsive DNA regulatory element. The focus of this proposal is to determine how this factor, CBF I, activates transcription. The approach that will be taken is based on two important observations: 1)the transcriptional activity of CBF1 in yeast requires the action of at least three transcriptional adaptor proteins, ADA2, ADA3, and GCN5; and 2) Arabidopsis encodes a homolog of the yeast ADA2 protein. Thus, plants may have a transcriptional adaptor system related to the ADA complex of yeast and this system may be involved in cold- and drought-regulated gene expression. These hypotheses will be tested by: 1) defining the boundaries and key residues of the CBF1 activation domain; 2) determining whether the CBF1 activation domain interacts directly with the Arabidopsis ADA2 protein and if so, whether the interaction is affected by temperature or dehydration stress; 3) determining whether the Arabidopsis ADA2 protein interacts with homologs of the ADA3 and GCN5 proteins or with novel plant adaptor proteins; and 4) assessing the extent to which the Arabidopsis ADA2 protein is involved in plant growth and development and response to various environmental stresses. The results of this project will provide fundamental new information on the nature of the proteins with which plant transcriptional activators interact to stimulate transcription, an area about which virtually nothing is known in plants. In addition, they will provide significant new informat ion about cold-regulated gene expression and will open the door to a more globally integrated understanding of plant gene regulation. Plants respond to cold stress by synthesizing specific proteins. This regulatory response is caused by changes in gene expression at the level of transcription, the process by which DNA is copied into RNA. These transcriptional changes are caused by interactions between proteins, called transcription factors, and DNA. This project will study proteins that interact with transcription factors, called transcriptional adaptors, during cold stress. Analogous proteins have been discovered in yeast, but this is the first indication that they exist in plants. This project will determine whether these proteins play a similiar role in plants and define the parts of the transcriptional adaptor molecule that are critical for interacting with the cold-activated transcription factor. This understanding may contribute to our understanding of how plants adapt to cold.