CRISPR-Cas mediated genome engineering of cyanobacteria

Over the past decade, several cyanobacterial strains have emerged as exciting model systems for unraveling important biological process like photosynthesis and nitrogen fixation. In parallel, novel strains are being developed as platforms for production of various value-added products. To meet either of these goals, synthetic biology tool development has been prioritized, and among many such tools, CRISPR-mediated genome editing tools distinctly hold the potential to revolutionize cyanobacterial research. This chapter reviews our current understanding of the existing and emerging CRISPR-based technologies and their potential application for advanced genome editing in cyanobacterial strains of interest. CRISPR-based tools have gained traction in cyanobacterial research for their ability to target the polyploid genomes in these organisms and generate fully segregated mutants in a remarkably short time. We discuss the native cyanobacterial CRISPR system and the promise they hold for use as precision tools for cyanobacterial genome editing. We elaborate the methodologies for the development of CRISPR-based markerless mutants in cyanobacteria as well as discuss strategies for large scale, regulated genome silencing with CRISPRi. We also highlight some of the emerging CRISPR tools that have shown promise in other prokaryotic and eukaryotic systems but are yet to be adapted for cyanobacterial research.