Abstract
Chloroplasts are photosynthetic organelle in plant cells, which are also involved in the synthesis of stress hormones such as jasmonic acid and salicylic acid, and production of reactive oxygen species (ROS). However, the role of chloroplasts in plant defense responses against biotic and abiotic stresses remains largely unknown. CAS is a Ca2+ binding protein localized in chloroplast thylakoid membrane and has been reported to be involved in the external Ca2+-induced generation of cytosolic Ca2+ signals and stomatal closure. We recently found that effecter-induced hypersensitive cell death (HR) was significantly delayed in CAS knockout mutants, while salt-induced chlorosis was promoted by CAS inactivation. To elucidate a role of CAS in plant immune responses, we examined the effects of knockdown and overexpression of CAS on flg22-induced defense gene expression. Here, we report that CAS is involved in the flg22-induced PR1 gene expression (salicylic acid pathway) in Arabidopsis.
