sRkB and sRkC RNA candidates from repetitive intergenic regions specific to P . abyssi genome. (A) Detection of sRkB and sRkC by Northern blotting. Source of RNAs, markers and sR26 loading control are as indicated in Figure 1B. (B) Gene maps drawn to scale. (ppp) and (p) represent tri- and mono-phosphate 5' ends, respectively. Three CR-RT-PCRs were performed using primer pairs designed to detect sRkB (R1, top panel) and sRkC (R2 and R3, bottom panel). In R2 and R3, two different primer pairs used to permit the complete mapping of the sRkC transcripts. (C) Native 6% PAGE of the CR-RT-PCR products using specific primers (Additional file 7 Table S2). Above the lanes, -/+ indicates mock control or treatment with tobacco acid pyrophosphatase (TAP).