Required for defense response to Xanthomonas campestris pv. vesicatoria (Xcv). In heterologous systems, confers resistance to bacterial pathogens such as Pseudomonas syringae pv. tomato but susceptibility to pathogenic oomycetes such as Hylaloperonospora parasitica when expressed in Arabidopsis thaliana. May be involved in the regulation of responses to bitoic and abiotic stresses. Homodimer and heterodimers. Mostly expressed in stems and flowers. In leaves by X.campestris pv. vesicatoria, faster during compatible than incompatible interactions. Induced in leaves by treatments with ethylene, methyl jasmonate (MeJA), abscisic acid (ABA), beta-amino-n-butyric acid (BABA), NaCl, mechanical wounding, and low temperature, but not with salicylic acid (SA). Susceptibility to X.campestris pv. vesicatoria is enhanced upon virus induced gene silencing (VIGS). Belongs to the Casparian strip membrane proteins (CASP) family.