The orthologue of the RNA chaperone Hfq is essential for cell motility of the cyanobacterium Synechocystis PCC 6803

The gene ssr3341 was previously suggested to encode an orthologue of the RNA chaperone Hfq in Synechocystis sp. strain PCC 6803. When a phototactic strain of this cyanobacterium was insertionally inactivated at ssr3341, the mutants were not transformable, and were rendered non-phototactic compared to the wild type. The loss of motility was complemented by re-introduction of the wild-type gene, correlated with the re-establishment of type IV pili on the cell surface. Microarray analyses revealed a small set of genes with drastically reduced transcript levels in the knock-out mutant over wild-type cells. Among the most strongly affected genes are with slr1667, slr1668, slr2015, slr2016 and slr2018 five genes which belong to two operons that previously were shown to be involved in motility and controlled by the SYCRP1-cAMP receptor protein. This fact constitutes a link between cAMP signalling, motility, and the involvement of RNA-based regulation. This is the first report demonstrating a functional role of Hfq in cyanobacteria. Keywords: comparative expression profiling Microarray experiments were carried out as two-color hybridizations on custom designed 8-pack 15K Synechocystis sp. microarrays (AMADID 016989) from Agilent Technologies (Santa Clara, USA).