UC San Diego

Arabidopsis thaliana Plant Elicitor Peptide 1 (AtPep1) is an endogenous peptide that interacts with its membrane embedded receptors PEPR1 and PEPR2 to amplify Damage- and Pathogen-associated molecular pattern (DAMP and PAMP)-triggered immunity (Huffaker et al., 2006; Ross et al., 2014). The Huffaker lab identified putative novel components regulating innate immune responses in Arabidopsis by examining the alterations in phosphorylation states of proteins after peptide treatment. In this study of AtPep1-triggered immunity, one of the identified candidates, calcium-dependent protein kinase 32 (CPK32), has been characterized. From previous studies and preliminary data, the structure and localization of CPK32 have been roughly established. However, the function of CPK32 in DAMP and PAMP-triggered immune responses has not been identified. In this thesis report, it was investigated how CPK32 affected Pep-induced plant defense and growth in Arabidopsis. This study focuses on characterizing early signaling events in the cpk32 knockout mutants, cpk32-1 and cpk32-2, including rapid burst of reactive oxygen species (ROS), activation of mitogen activated protein kinase (MAPK), and defense gene expression changes. To address the biological relevance and elucidate the function of CPK32 in plant resistance to bacteria and fungus, cpk32 mutants were infected with biotrophic and necrotrophic pathogens, Pseudomona syringae pv tomato DC30000 (Pst DC3000) and Botrytis cinerea (B. cinerea). Overall, the data obtained suggest that CPK32 is a negative regulator in AtPep1-induced immune responses.