Low Temperature Regulatory Circuits and Gene Regulons in Higher Plants

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Plants vary greatly in their responses to cold temperatures. At one extreme are plants from tropical and subtropical regions such as soybean and rice, which suffer injury when exposed to chilling temperatures between 0 and 12 degrees Celcius. In sharp contrast, plants from temperate regions are not only chilling tolerant, but many, such as Arabidopsis and wheat, can survive freezing after exposure to low nonfreezing temperatures, a phenomenon known as "cold acclimation." The overall goal of this project is to understand the "genomic" basis of cold tolerance. The specific focus will be to develop a more detailed understanding of how plants respond to low temperature in terms of altering gene expression. This emphasis is motivated by the recent demonstration in Arabidopsis that cold acclimation involves the action of cold-regulated genes including the CBF regulon, a group of genes that imparts freezing tolerance and is coordinately regulated by the CBF transcriptional activators. This project will comprise three related lines of investigation. In the first, a low temperature "wiring diagram" will be constructed that includes a definition of low temperature regulatory circuits and the gene regulons that they control. The second line of investigation will be to determine the similarities and differences of low temperature-regulated genes in plants that differ in freezing tolerance. The third line of investigation will be to determine whether the Arabidopsis CBF cold-response pathway is highly conserved in other plants and whether differences in plant cold tolerance can be traced to differences in CBF cold-response pathways. Comparative and functional genomics approaches will be used to address these issues including gene expression profiling using DNA microarrays. In sum, these lines of investigation will provide a deeper understanding of the "genomic mechanisms" that plants have evolved to cope with low temperature and have the potential to provide "genetic tools" to improve the cold tolerance of plants, traits of considerable agronomic and economic importance. In as much as the CBF regulon not only imparts freezing tolerance, but dehydration tolerance as well, the results of this project also have the potential to provide genetic tools to improve the drought and salinity tolerance of agriculturally important plants.Deliverables:Microarray data and other information about the project can be found at: http://aztec.stanford.edu/cold.