CCaMK-Mediated Changes During Bacterial and Fungal Symbioses

Washington State University, Pullman WA

Investigators

Abstract

A Ca2+/calmodulin-dependent protein kinase (CCaMK) has been implicated as a key player in the signal transduction cascade that follows perception of nitrogen fixing bacterial symbionts by plant roots and leads to the establishment of nitrogen-fixing root nodules. This project seeks to determine the role of this kinase in roots as signals from potential symbionts are received and transduced to downstream effectors involved in nodule formation. CCaMK, a multi-functional protein, is characterized by the presence of a kinase domain, an autoinhibitory domain, a calmodulin-binding domain and a neural visinin-like Ca2+-binding domain in a single polypeptide. CCaMK undergoes two steps of Ca2+ regulation, first directly through its Ca2+-binding domain and then indirectly through its Ca2+/calmodulin-binding domain. Recent investigations have revealed that CCaMK plays critical roles in both bacterial and fungal symbioses. During bacterial interactions which lead to nitrogen fixation, CCaMK acts immediately downstream of Ca2+ oscillations triggered in root hair cells by the bacterially produced signaling molecule, Nod factor. The immediate goal of this investigation is to study how the structural changes of CCaMK control bacterial invasion and the resulting symbiotic relationship. Furthermore, the project will also seek to identify and characterize CCaMK's potential downstream interaction partner(s). Genetic studies indicate that CCaMK is at a critical juncture of a branch point in the signaling pathway which mediates the interaction of plants with their symbionts: one branch leads to nodulation and the other to mycorrhizal infection. Hence, this project may lead to new insights into fungal as well as bacterial symbioses. This project will use genetic, biochemical and cellular approaches to address a seminal question in the area of plant:microbe interactions. In addition to its agricultural and ecological significance the broader impacts of the project include training undergraduates, graduate students and postdocs. Training of minorities and women who are interested in science will be emphasized. On-site participants will experience the atmosphere of an active biotechnology research laboratory. To reach a wider audience, the WSU team will also use the Washington State Higher Education Telecommunication System and organize onsite workshops.