Figure 2.

Accumulation of 33 abundant sRNAs in Synechocystis sp. PCC 6803 under nine different growth conditions. (A and B) The 10 most abundant sRNAs and an additional 23 abundant sRNAs with interesting expression patterns were chosen. The relative abundance of sRNAs was estimated by the number of associated reads in dRNA-seq analysis (Kopf et al.2014a). Selected sRNAs with condition-dependent high accumulation were independently verified. These include the high abundance of PsrR1 in high light conditions (Mitschke et al.2011b; Kopf et al.2014a), IsaR1 in the -Fe condition (Hernandez-Prieto et al.2012; Kopf et al.2014a), NsiR4, CsiR1 and PsiR1 during nitrogen, carbon or phosphate depletion (Kopf et al.2014a) and the accumulation of SyR9 as part of the two-gene locus for alkane biosynthesis (Klähn et al.2014). High PsrR1 expression under high light is functionally relevant (Georg et al.2014). By analogy, other stress-inducible sRNAs are top candidates as regulatory molecules under each respective condition. Some identified sRNAs may encode short peptides. The phosphate stress-inducible sRNA PsiR1 contains two short reading frames (see also Fig. 6), and the high light-inducible sRNA HliR1 contains a short reading frame with 33 of its 37 residues conserved in the gene product D082_13860 in the sister strain Synechocystis sp. PCC 6714 (Kopf et al.2014b). (B) Enlargement of the 23 less abundant sRNAs from panel (A) for better resolution. Note that the sequences of the 33 transcripts were inferred from transcriptome analysis (Mitschke et al.2011b; Kopf et al.2014a) and are available for download (Supplemental file 1).