Diverse Peptide Hormones Affecting Root Growth Identified in the Medicago truncatula Secreted Peptidome

作者：Neha Patel, Nadiatul A. Mohd‐Radzman, Leo Corcilius, Ben Crossett, Angela Connolly, Stuart J. Cordwell, Ariel Ivanovici, Katia Taylor, James T. Williams, Steve Binos, Michael Mariani, Richard J. Payne, Michael A. Djordjevic · 发表于：Molecular & Cellular Proteomics · 年份：2017 · DOI：10.1074/mcp.ra117.000168 · 被引用次数：78 · 研究领域：Plant Reproductive Biology、Biochemical and Structural Characterization、Plant Molecular Biology Research

Multigene families encoding diverse secreted peptide hormones play important roles in plant development. A need exists to efficiently elucidate the structures and post-translational-modifications of these difficult-to-isolate peptide hormones in planta so that their biological functions can be determined. A mass spectrometry and bioinformatics approach was developed to comprehensively analyze the secreted peptidome of Medicago hairy root cultures and xylem sap. We identified 759 spectra corresponding to the secreted products of twelve peptide hormones including four CEP ( C -TERMINALLY E NCODED P EPTIDE), two CLE ( CL V3/ E NDOSPERM SURROUNDING REGION RELATED) and six XAP ( X YLEM SAP A SSOCIATED P EPTIDE) peptides. The MtCEP1, MtCEP2, MtCEP5 and MtCEP8 peptides identified differed in post-translational-modifications. Most were hydroxylated at conserved proline residues but some MtCEP1 derivatives were tri-arabinosylated. In addition, many CEP peptides possessed unexpected N - and C -terminal extensions. The pattern of these extensions suggested roles for endo- and exoproteases in CEP peptide maturation. Longer than expected, hydroxylated and homogeneously modified mono- and tri-arabinosylated CEP peptides corresponding to their in vivo structures were chemically synthesized to probe the effect of these post-translational-modifications on function. The ability of CEP peptides to elevate root nodule number was increased by hydroxylation at key positions. MtCEP1 peptides with N...