An optimized RNA amplification method for prokaryotic expression profiling analysis

Conventional prokaryotic RNA labeling method usually requires large amounts of starting materials and tends to generate high background signals. Recently, two novel methods based on amplification systems were introduced. Here, we compared three alternative strategies: direct labeling method, ployadenylation-involved oligo-dT priming amplification method and random priming amplification method (hereafter referred to as DL, PAOD and RPA method in this article) for prokaryotic RNA labeling employing the expression profiling investigation in Escherichia coli (E. coli) heat shock model. To identify an optimal RNA labeling method for prokaryotic microarray analysis, experiments were performed with starting RNA obtained from E.coli growing at control (37°C) or heat shock (43°C) condition. We employed 0.5 μg of total RNA for a single round of amplification using PAOD and RPA methods coupling to IVT to generate cDNA targets. In addition, an approach using DL method was also performed. Three types of cDNA mixtures containing Cy5-labeled (or Cy3-labeled) control DNA and Cy3-labeled (or Cy5-labeled) DNA targets were hybridized with E.coli microarrays in a dye-swap strategy. Replicate experiments were conducted from the same batch of total RNA to assess technique reproducibility of each approach.