Systems Analysis of Calmodulin and the CBP60 Gene Family in Control of Plant Immunity

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

Many proteins are controlled by binding of a small protein called calmodulin. In most cases, calmodulin must bind calcium ions, which changes the shape of the calmodulin, before it can bind to other proteins. In this way, calmodulin transmits information about the presence of calcium ions, which control many biological processes. Some calmodulin-binding proteins are important for control of immune responses in plants. In this project, several aspects of calcium and calmodulin function in plant immunity will be investigated. First, the molecular mechanisms by which these proteins control immunity will be determined. Second, a quantitative model describing their positive and negative effects will be developed and used to understand possible benefits of having both positively and negatively acting members in this protein family. Third, a broader understanding of the roles of calcium and calmodulin will be gained by testing other calmodulin binding proteins for roles in plant immunity and determining which immune responses they affect. The project includes a program to improve the teaching skills of graduate students and post-doctoral fellows. Undergraduates will receive research experience. CBP60a, CBP60g and SARD1 (which does not bind calmodulin) play critical roles in modulating the production of the defense hormone salicylic acid (SA) and controlling gene expression following pathogen recognition. Thus, these proteins appear to link the Ca2+ influx to downstream responses. This project includes three aims that seek insight into how Ca2+ and calmodulin control plant immunity: 1-Determine the biochemical mechanism of CBP60 immune function. CBP60 proteins may bind directly to promoters of regulated genes, or to transcription factors. It is possible that they bind to certain calmodulin-like proteins that are negative regulators of immunity. These ideas will be tested using various assays for protein-protein interactions and protein-DNA binding. 2-Characterize the effect on immune system stability of CBP60 proteins acting positively and negatively on activation of defenses. The existence of both positively and negatively-acting CBP60 family members may improve system stability and/or provide resilience in the face of pathogen attack. These ideas will be tested using quantitative systems modeling of the CBP60 signaling node. 3-Identify components of the protein network mediating Ca2+ control of immune signaling. Many proteins besides CBP60s may be involved in transduction of the Ca2+ signal. Interactions among pathogen-inducible calmodulin-like proteins and other proteins annotated as having Ca2+-related functions will be tested. Plants with mutations in these genes will be screened for altered immunity phenotypes.