Functions of the Acidic Ribosomal Proteins of Maize

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9315015 Bailey-Serres Protein synthesis is a multi-step process that is regulated at numerous levels in maize as well as in all other organisms. The hypoxic (low-oxygen) stress response of seedling roots involves the rapid inhibition of initiation, followed by selective initiation and elongation of mRNA translation. The hypoxic stress response provides a model for studying modulation of protein synthesis under low energy conditions. This project focuses on modifications of acidic ribosomal proteins (ARPs) in response to hypoxia. Three acidic-phosphorylated proteins, known as P0, P1 and P2, are present as a multimeric structure in the active site of the ribosome where interactions between mRNA, tRNA and translation factors occur during the late-initiation, elongation and termination phases of translation. The biochemical objectives are to identify P0, P1 and P2 of maize, analyze the stoichiometry of the three-types of ARPs in monoribosomes and polyribosomes of aerobic and hypoxic roots, characterize the in vivo phosphorylation of ARPs under control and hypoxic conditions, and analyze other modifications of ARPs in response to hypoxia. The molecular objectives are to identify and sequence the genes encoding the ARPs of maize, and to initiate site-directed mutagenesis of the phosphorylation sites of the ARPs genes. The long-term goal is to test the role of ARP modification in an in vitro translation system from maize root tips. These experiments will provide the foundation for the elucidation of ribosome structure-function relationships in mechanisms of protein synthesis in higher plants. This project involves a collaboration with Dr. Estela Sanchez de Jimenez at National Autonomous University of Mexico, Mexico City. ***