Parallel global profiling of plant TOR dynamics reveals a conserved role for LARP1 in translation
M Regina Scarpin,
Samuel Leiboff,
Jacob O Brunkard
Affiliations
M Regina Scarpin
Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, United States; Plant Gene Expression Center, U.S. Department of Agriculture Agricultural Research Service, Albany, United States
Samuel Leiboff
Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, United States; Plant Gene Expression Center, U.S. Department of Agriculture Agricultural Research Service, Albany, United States; Department of Botany and Plant Pathology, Oregon State University, Corvallis, United States
Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, United States; Plant Gene Expression Center, U.S. Department of Agriculture Agricultural Research Service, Albany, United States; Laboratory of Genetics, University of Wisconsin—Madison, Madison, United States
Target of rapamycin (TOR) is a protein kinase that coordinates eukaryotic metabolism. In mammals, TOR specifically promotes translation of ribosomal protein (RP) mRNAs when amino acids are available to support protein synthesis. The mechanisms controlling translation downstream from TOR remain contested, however, and are largely unexplored in plants. To define these mechanisms in plants, we globally profiled the plant TOR-regulated transcriptome, translatome, proteome, and phosphoproteome. We found that TOR regulates ribosome biogenesis in plants at multiple levels, but through mechanisms that do not directly depend on 5′ oligopyrimidine tract motifs (5′TOPs) found in mammalian RP mRNAs. We then show that the TOR-LARP1-5′TOP signaling axis is conserved in plants and regulates expression of a core set of eukaryotic 5′TOP mRNAs, as well as new, plant-specific 5′TOP mRNAs. Our study illuminates ancestral roles of the TOR-LARP1-5′TOP metabolic regulatory network and provides evolutionary context for ongoing debates about the molecular function of LARP1.
