title: Quantitative phosphoproteomic analysis of soybean root hairs inoculated with Bradyrhizobium japonicum.
abstract: Root hairs are single hair-forming cells on roots that function to increase root surface area, enhancing water and nutrient uptake. In leguminous plants, root hairs also play a critical role as the site of infection by symbiotic nitrogen fixing rhizobia, leading to the formation of a novel organ, the nodule. The initial steps in the rhizobia-root hair infection process are known to involve specific receptor kinases and subsequent kinase cascades. Here, we characterize the phosphoproteome of the root hairs and the corresponding stripped roots (i.e. roots from which root hairs were removed) during rhizobial colonization and infection to gain insight into the molecular mechanism of root hair cell biology. We chose soybean (Glycine max L.), one of the most important crop plants in the legume family, for this study because of its larger root size, which permits isolation of sufficient root hair material for phosphoproteomic analysis. Phosphopeptides derived from root hairs and stripped roots, mock inoculated or inoculated with the soybean-specific rhizobium Bradyrhizobium japonicum, were labeled with the isobaric tag eight-plex iTRAQ, enriched using Ni-NTA magnetic beads and subjected to nanoRPLC-MS/MS1 analysis using HCD and decision tree guided CID/ETD strategy. A total of 1625 unique phosphopeptides, spanning 1659 nonredundant phosphorylation sites, were detected from 1126 soybean phosphoproteins. Among them, 273 phosphopeptides corresponding to 240 phosphoproteins were found to be significantly regulated (>1.5-fold abundance change) in response to inoculation with B. japonicum. The data reveal unique features of the soybean root hair phosphoproteome, including root hair and stripped root-specific phosphorylation suggesting a complex network of kinase-substrate and phosphatase-substrate interactions in response to rhizobial inoculation.
authors: Division of Plant Sciences, C.S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211, USA.
authors: Tran Hong Nha
authors: TH
authors: Nguyen
authors: Laurent
authors: L
authors: Brechenmacher
authors: Joshua T
authors: JT
authors: Aldrich
authors: Therese R
authors: TR
authors: Clauss
authors: Marina A
authors: MA
authors: Gritsenko
authors: Kim K
authors: KK
authors: Hixson
authors: Marc
authors: M
authors: Libault
authors: Kiwamu
authors: K
authors: Tanaka
authors: Feng
authors: F
authors: Yang
authors: Qiuming
authors: Q
authors: Yao
authors: Ljiljana
authors: L
authors: Pasa-Tolić
authors: Dong
authors: D
authors: Xu
authors: Henry T
authors: HT
authors: Nguyen
authors: Gary
authors: G
authors: Stacey
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism; D020369:Bradyrhizobium / Q000187:drug effects / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D020440:Gene Duplication; D054884:Host-Pathogen Interactions / Q000187:drug effects; D013058:Mass Spectrometry; D046913:Medicago truncatula / Q000378:metabolism; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000187:drug effects; D010748:Phosphopeptides / Q000737:chemistry / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D055170:Plant Root Nodulation / Q000187:drug effects; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000382:microbiology*; D011494:Protein Kinases / Q000378:metabolism; D020543:Proteome / Q000737:chemistry / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D013025:Glycine max / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D013223:Statistics as Topic; D014867:Water
chemical_list: D010748:Phosphopeptides; D010750:Phosphoproteins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D020543:Proteome; D014867:Water; D011494:Protein Kinases