A simple, economical and reproducible protein extraction protocol for proteomics studies of soybean roots

Sample preparation is a critical step in two-dimensional gel electrophoresis (2-DE) of plant tissues. Here we describe a phenol/SDS procedure that, although greatly simplified, produced well-resolved and reproducible 2-DE profiles of protein extracts from soybean [Glycine max (L.) Merril] roots. Extractions were made in three replicates using both the original and simplified procedure. To evaluate the quality of the extracted proteins, ten spots were randomly selected and identified by mass spectrometry (MS). The 2-DE gels were equally well resolved, with no streaks or smears, and no significant differences were observed in protein yield, reproducibility, resolution or number of spots. Mass spectra of the ten selected spots were compared with database entries and allowed high-quality identification of proteins. The simplified protocol described here presents considerable savings of time and reagents without compromising the quality of 2-DE protein profiles and compatibility with MS analysis, and may facilitate the progress of proteomics studies of legume-rhizobia interactions.