The plasma membrane (PM) serves as the point of contact between cells and the outside environment. As such, changes in the PM proteome are an important component of understanding cellular responses to a diverse array of stimuli. However, intricate sample handling to enrich PM proteomes by traditional methods is both technically challenging and time consuming. Here, we describe a simplified method for decreasing the representation of other membrane-containing organelles such as the endoplasmic reticulum, plastids and mitochondria from crude microsomal membrane isolations. The decrease in other organellar proteomes results in an increase in both the total number of PM proteins and the number of spectra identified from these proteins representing the PM proteome. Therefore, this strategy represents a simple and rapid method for enriching PM proteins from Arabidopsis cell cultures for proteomic analyses.

Plants are continuously exposed to changing environmental conditions and must, as sessile organisms, possess sophisticated acclimative mechanisms. To gain insight into systemic responses to local virus infection or wounding, we performed comparative LC-MS/MS protein profiling of distal, virus-free leaves four and five days after local inoculation of Arabidopsis thaliana plants with either Oilseed rape mosaic virus (ORMV) or inoculation buffer alone. Our study revealed biomarkers for systemic signaling in response to wounding and compatible virus infection in Arabidopsis, which should prove useful in further addressing the trigger-specific systemic response network and the elusive systemic signals. We observed responses common to ORMV and mock treatment as well as protein profile changes that are specific to local virus infection or mechanical wounding (mock treatment) alone, which provides evidence for the existence of more than one systemic signal to induce these distinct changes. Comparison of the systemic responses between time points indicated that the responses build up over time. Our data indicate stress-specific changes in proteins involved in jasmonic and abscisic acid signaling, intracellular transport, compartmentalization of enzyme activities, protein folding and synthesis, and energy and carbohydrate metabolism. In addition, a virus-triggered systemic signal appears to suppress antiviral host defense.

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