During the past decade peptide signals have been recognized as important regulatory molecules involved in plant growth and development, reproduction and defense. Similar to polypeptide hormones in other eukaryotes, most plant regulatory peptides are extracellular signals derived from larger precursor proteins. Although thoroughly studied in animal systems and yeast, the regulation of synthesis, processing, storage and secretion of peptide signals in plants is poorly understood. The main goal of this research is to establish the intracellular pathway for the biogenesis of the defense-related AtPep1 peptide signal in Arabidopsis. AtPep1 is derived from a larger prohormone precursor (PROPEP1) that appears not to be synthesized through the secretory pathway. PROPEP1 processing enzymes have not been identified, and the mechanism for AtPep1 deposition in the cell wall apoplast to interact with a membrane receptor is not known. The research plan will incorporate the use of a novel biarsenical-tetracysteine (TC) labeling system for live-cell fluorescent imaging that offers unique advantages and capabilities to study the dynamics of peptide biogenesis, correlated with ultrastructural analysis by electron microscopy and immunocytochemistry. The proposed study represents the first complete characterization of the biogenesis of a peptide hormone in plants. The results will be a foundation for future work on the identification of the processing enzymes, and the isolation of the molecular carriers involved in peptide transport, using a combination of pharmacological, biochemical and functional genomic tools.
Broader impact
Deciphering non-classical mechanisms involved in the processing and secretion of regulatory peptides will improve our understanding of the biology of peptide hormones in plants, and the evolution of defense peptide signaling in eukaryotes. Due to the role of AtPep1 in innate immunity and the presence of AtPep1 homologues in crop plants, the results of this research may have important applications in the future improvement of plant resistance against insect and pathogen attacks through crop biotechnology. This study may result in a new application of the TC tagging system to study peptide hormone biogenesis in plants and other organisms. The proposed research activities will be carried out with the participation of undergraduate students from underrepresented groups, fostering education and community outreach. The research will provide undergrads with intellectual challenges and meaningful learning experiences in plant biology and the use of modern cellular imaging and molecular biology techniques.
