text: Among the diverse range of defense strategies plants utilize against pathogens, Ca signaling is very common. Free Ca levels in the cytoplasm increases in response to a pathogenic infection. Ca signatures of this nature usually activate the plant defense system by inducing defense-related genes and the hypersensitive cell death. CaMs, CMLs and CaM-binding proteins are some of the recently identified elements of the plant defense signaling pathways. Several CML genes in tobacco, bean and tomato are responsive to pathogens. CML43 is a CaM-related protein that, as isolated from APR134 gene in the disease-resistant leaves of Arabidopsis for gene expression analysis, is rapidly induced when the leaves are inoculated with Pseudomonas syringae. These genes are also found in tomatoes (Solanum lycopersicum). The CML43 from the APR134 also binds to Ca ions in vitro which shows that CML43 and APR134 are, hence, involved in the Ca-dependent signaling during the plant immune response to bacterial pathogens. The CML9 expression in Arabidopsis thaliana is rapidly induced by phytopathogenic bacteria, flagellin and salicylic acid. Expression of soybean SCaM4 and SCaM5 in transgenic tobacco and Arabidopsis causes an activation of genes related to pathogen resistance and also results in enhanced resistance to a wide spectrum of pathogen infection. The same is not true for soybean SCaM1 and SCaM2 that are highly conserved CaM isoforms. The AtBAG6 protein is a CaM-binding protein that binds to CaM only in the absence of Ca and not in the presence of it. AtBAG6 is responsible for the hypersensitive response of programmed cell death in order to prevent the spread of pathogen infection or to restrict pathogen growth. Mutations in the CaM binding proteins can lead to severe effects on the defense response of the plants towards pathogen infections. Cyclic nucleotide-gated channels (CNGCs) are functional protein channels in the plasma membrane that have overlapping CaM binding sites transport divalent cations such as Ca. However, the exact role of the positioning of the CNGCs in this pathway for plant defense is still unclear.