title: Absolute protein quantification by LC/MS(E) for global analysis of salicylic acid-induced plant protein secretion responses.
abstract: The plant cell wall is a dynamic cellular compartment consisting of a complex matrix of components that can change dramatically in response to environmental stresses. During pathogen attack, for instance, a wide spectrum of proteins that participate in various sequential processes involved in plant defense is secreted into the cell wall. In this study, a mass spectrometry, data-independent acquisition approach known as LC/MS (E) was used to assess temporal changes in the cell wall proteome in response to different levels of an endogenous inducer of plant disease defense responses, salicylic acid (SA). LC/MS (E) was used as a label-free method that enabled simultaneous protein identification and absolute femtomole quantification of each protein secreted into the extracellular matrix. A total of 74 secreted proteins were identified, 63 of which showed increased specific secretion in response to SA. A majority of this induced secretion occurred within 2 h of treatment, indicating that many proteins are involved in the early stages of plant defenses. We also identified a number of apparently nonclassically secreted proteins, suggesting that, as in many nonplant systems, Golgi/ER-independent mechanisms exist for plant protein secretion. These results provide new insight into plant apoplastic defense mechanisms and demonstrate that LC/MS (E) is a powerful tool for obtaining both relative and absolute proteome-scale quantification that can be applied to complex, time- and dose-dependent experimental designs.
authors.affiliation: Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina 27695-7609, USA.
authors.forename: Fang-yi
authors.initials: FY
authors.lastname: Cheng
authors.forename: Kevin
authors.initials: K
authors.lastname: Blackburn
authors.forename: Yu-min
authors.initials: YM
authors.lastname: Lin
authors.forename: Micheal B
authors.initials: MB
authors.lastname: Goshe
authors.forename: John D
authors.initials: JD
authors.lastname: Williamson
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods*; D019295:Computational Biology; D013058:Mass Spectrometry / Q000379:methods*; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D020543:Proteome; D040901:Proteomics / Q000379:methods*; D020156:Salicylic Acid / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D010940:Plant Proteins; D011506:Proteins; D020543:Proteome; D020156:Salicylic Acid