Discovery and Application of Stress-Responsive sRNAs in Cyanobacteria.

Bacterial small regulatory RNAs (sRNAs) are noncoding molecules with a typical length of 50-300 nt. In recent years, sRNAs have drawn notable attention due to their participation in various bacterial biological processes, such as plasmid control, viral replication, bacterial virulence, and quorum sensing. In addition, there has been a gradual realization that sRNAs play important roles in the response to various stress perturbations. Gram-negative cyanobacteria are autotrophic prokaryotes that perform oxygenic photosynthesis, which makes them promising renewable chassis for the production of green fuels and chemicals as an alternative to the traditional biomass-based "microbial cell factory." Nevertheless, the survival and growth of cyanobacteria are affected by multiple stressors derived from the environment and from the end products; these organisms synthesize, limiting the potential applications of cyanobacteria-based biotechnology. Given the importance of sRNAs in metabolic regulation, the identification of cyanobacterial sRNAs related to stress responses could be vital for further improving the stress tolerance of cyanobacterial chassis. Toward this goal, recent studies have described the discovery and functional characterization of a series of sRNAs related to stress responses, including responses to oxidative stress, salt, nutrient starvation, and ethanol and 1-butanol stress conditions. In this chapter, we critically review recent efforts to identify cyanobacterial sRNAs involved in stress responses and their potential applications for modifying cyanobacterial tolerance.