Ethylene production in Synechocystis sp. PCC 6803 promotes phototactic movement

Ethylene is a gaseous signal sensed by plants and bacteria. Heterologous expression of the ethylene-forming enzyme (EFE) from Pseudomonas syringae in cyanobacteria leads to the production of ethylene under photoautotrophic conditions. The recent characterization of an ethylene responsive signaling pathway affecting phototaxis in the cyanobacterium Synechocystis sp. PCC 6803 implies that biotechnologically relevant ethylene synthesis may induce regulatory processes which are not related to changes in the metabolism. Here we provide data that endogenously produced ethylene accelerates movement of cells towards light. Microarray analysis demonstrates that ethylene deactivates transcription from the csiR1/lsiR promoter which is under control of the two-component system consisting of the ethylene and UV-A-sensing histidine kinase UirS and the DNA-binding response regulator UirR. Surprisingly, only very few other transcriptional changes were detected in the microarray analysis providing no direct hints to possible bottlenecks in phototrophic ethylene production. We performed whole-genome transcript profiling of an ethylene producing strain of Synechocystis sp. PCC 6803.