Characterization of Arabidopsis CALMODULIN-LIKE genes involved in fine-tuning plant immune signaling    
Y. LU (1), W. Truman (2), G. Bethke (1), J. Glazebrook (1) (1) University of Minnesota, Twin Cities, U.S.A.; (2) Institute of Plant Genetics of the Polish Academy of Sciences, Poland

The genome of Arabidopsis thaliana contains 50 genes encoding CALMODULIN-LIKE (CML) proteins. Over half of them have at least one paralog that emerged within the Brassicaceae family. This lineage-specific expansion suggests roles in adaptive responses to environmental stimuli, such as immune responses to pathogen attack. Mutations in 11 CML genes altered pathogen growth. CML46 and CML47 appear to be negative regulators of immunity, and they are tightly co-expressed with SID2, CBP60g and SARD1, genes with positive effects on immune signaling including production of salicylic acid. In cml46 cml47 double mutant plants, growth of the bacterial pathogen Pseudomonas syringae is nearly 10-fold lower than in wild-type plants. We suspect that this enhanced resistance may be partially due to slower decline of defense gene expression following the initial induction. Interestingly, the negative immunity effects of CML46 and CML47 are additive to the effect of a known negative regulator that requires calmodulin binding for its function, CBP60a, as combining the mutations in these three genes leads to a further decrease in pathogen growth. We hypothesize that CML46 and CML47 are components of a recently-evolved incoherent feed-forward loop regulatory circuit that is crucial for robust induction as well as steady control of plant immune signaling. Additional data from time course marker gene expression experiments and transcriptome-profiling would allow testing of this hypothesis.

Abstract Number: P16-458
Session Type: Poster