A MAP kinase cascade downstream of ERECTA and ERECTA-like receptors in regulating plant development

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Intellectual merit: Besides cell differentiation, stage-specific and localized cell division is also critical to the formation of normal tissues, organs, and organisms. The highly coordinated cell differentiation and proliferation events during growth and development illustrate the importance of cell-cell communication, which is carried out by cell surface receptors/sensors and intracellular signaling components. In Arabidopsis, ERECTA (ER), a receptor-like kinase, and its homologs (ERL1 and ERL2) play important roles in these processes. Their mutation alters both the architecture and the reproduction of the plant. Similar to er or er/erl1/erl2 mutant plants, loss-of-function of MPK3 and MPK6, two Arabidopsis mitogen-activated protein kinases (MAPKs), or their upstream MAPKKs (MKK4/MKK5) also resulted in similar phenotypes. Genetic analysis demonstrated that the gain-of-function MAPKK transgene can rescue the loss-of-function er or er/erl1/erl2 mutants, suggesting that MPK3/MPK6 function downstream of ER/ERL1/ERL2 receptors. The goal of this project is to understand the molecular mechanism underlying the function of MPK3/MPK6 in the regulation of localized cell division. In addition, the MAPKK kinase(s) upstream of the MKK4/MKK5-MPK3/MPK6 module will be identified. A combinatory approach will be employed to reach these goals. Defining a specific MAPK cascade downstream of the well-characterized ER/ERL1/ERL2 receptor-like kinases is important to our understanding of cell-cell communication. The identification of new components downstream of MPK3/MPK6 in the ER/ERL1/ERL2 pathway will reveal the molecular mechanism underlying their role in the localized cell division. The research will also reveal the functional diversity and signaling specificity of MPK3 and MPK6. The tools generated in this project will have broad applications and will be shared with other groups. Broader impacts: This project will use an integrative approach to understand the roles of a MAPK cascade and its upstream receptor-like kinases in coordinating plant development, which will serve as an excellent training environment for students and postdoctoral fellows. Training in use of integrative approaches to the study of biological phenomena is critical to the advancement of post-genome biology. In addition to scientific methodology, students/post-docs will also receive training in ethics and career development. Students (both graduate and undergraduate) and post-docs from under-represented groups will be actively recruited by participating in institutional programs that reach out to minorities. Post-docs involved in the project will follow a career development plan supported by the research training in the lab, student mentoring experiences, and professional development training. Understanding the signal transduction pathways and the identification of important regulators of plant growth and development could positively impact food/feed/biofuel production, which is important to sustain the increasing world population.