Yfr20 – the first light sensing non-coding RNA in Prochlorococcus marinus

Yfr20 is a unique non-coding RNA (ncRNA) in Prochlorococcus marinus, occurring in all sequenced high light-adapted strains [2]. Sequence alignments revealed two conserved sequence motifs. Putative interaction partners for conserved sequence motif 1 have been predicted in various Prochlorococcus strains based on computational analysis using IntaRNA [1].

Yfr20 has a negative impact on the translation of photosynthesis-related gene psb27. For regulatory interaction the conserved sequence motif, the accessibility of the seed region, and the secondary structure of target-regulator interaction are crucial.

Yfr20 represses psb27, which facilitates the integration of the water cleaving manganese cluster into the photosystem II complex. Because the expression of Yfr20 increases under high light stress and because Yfr20 only occurs in high light-adapted Prochlorococcus strains, Yfr20 might be involved in a signaling chain leading to modulation of the photosynthetic apparatus in a light intensity sensitive manner.

Genomic island V, in which the Yfr20 gene is located, appears to be relevant for the adaptation to different light conditions, which is additionally supported by the clustering of other light stress-related genes in this region. Genomic island V provides an interesting parallel to the relevance of genomic island-encoded ncRNA modulators of pathogenicity in pathogenic bacteria.