Research PGR: The Temperature-Immunity Nexus: Activation of Immunity by Low Temperature

Michigan State University, East Lansing MI

Investigators

Abstract

Plant diseases routinely cause significant losses in crop productivity. Thus, a fundamental goal of plant biology research is to identify genes that impart immunity against plant pathogens and to determine how they are regulated in response to environmental stimuli. Much has been learned about the nature of immunity genes and how they are regulated in response to pathogen attack; i.e., in response to biotic stress. However, recent studies have established that immunity genes can also be induced in response to abiotic stress, namely cold temperatures. In this proposal, the investigators will study this temperature-immunity nexus: how plant immunity is regulated by temperature. This phenomenon has received relatively little attention, but has been observed in crop and other plant species indicating that it may be an underappreciated highly conserved “preemptive” survival strategy; i.e., that plant immunity is activated in response to an abiotic stress that otherwise has the potential to increase the susceptibility of the plant to infection by pathogens. Given the ever-increasing concerns about climate change and the possible negative effects that these changes could have on crop productivity, it is of great importance to understand the connectivity between abiotic and biotic regulation of immunity genes as such information has the potential to be used to develop novel approaches to enhance plant resilience to environmental stresses. The Arabidopsis Calmodulin-binding Transcription Activator (CAMTA) transcription factors are master regulators of salicylic acid (SA)-mediated immunity. In healthy plants grown at moderate temperature (ca. 22C), the CAMTA proteins repress expression of SA-immunity genes. However, when plants are exposed to pathogens—a biotic stress—or, as has recently been demonstrated by this research team, low temperature (ca. 4C)—an abiotic stress—the CAMTA “brake” is “disabled” resulting in the induction of defense genes. A fundamental goal of this project is to determine how the repression activity of the Arabidopsis CAMTA3 protein is regulated by temperature. In particular, a combination of biochemical, proteomic, genetic and genomic approaches will be used to determine: 1) how the CAMTA3 protein represses expression of target genes at moderate temperature; 2) how low temperature suppresses CAMTA3 repression activity; and 3) whether abiotic factors other than low temperature can inactivate the CAMTA3 brake. An additional integral component of this project is to extend the studies on CAMTA regulation of immunity genes in Arabidopsis to a range of important crop species and to determine the extent to which regulation of immunity in response to low temperature and other abiotic stresses is conserved in plants. Taken together, the results from these lines of investigation promise to expand our knowledge of the basic Rules of Life that govern host defense mechanisms in plants. This award was co-funded by the Plant Genome Research Program and Plant Biotic Interactions Program. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.