Repression and De-repression of Gene Expression in the Plant Immune Response: The Complexity of Modulation by Ca2+ and Calmodulin

Recent reports demonstrate a role of calmodulin (CaM)-binding DNA-binding proteins (transcription factors [TFs]) as repressors of the plant immune response through their interactions with promoters of a number of target genes. However, the role of Ca2+ in gene repression has not been tested. Thus, to infer the function of such TFs as repressors of transcription prior to pathogen attack raises questions about the role of Ca2+ in this transcription repression and subsequently in de-repression upon pathogen attack.