The Response Regulator Npun_F1278 is Essential for Scytonemin Biosynthesis in the Cyanobacterium Nostoc Punctiforme ATCC 29133

Following exposure to long-wavelength ultraviolet radiation (UVA), some cyanobacteria produce the indole-alkaloid sunscreen scytonemin. The genomic region associated with scytonemin biosynthesis in the cyanobacterium Nostoc punctiforme includes 18 adjacent co-transcribed genes. A two-component regulatory system (Npun_F1277 and Npun_F1278) directly upstream from the biosynthetic gene cluster was identified through comparative genomic analysis and is likely involved in scytonemin regulation. In this study, the response regulator Npun_F1278 was evaluated for its ability to regulate scytonemin biosynthesis using a mutant strain of N. punctiforme deficient in this gene, hereafter strain Δ1278. Following UVA radiation, the typical stimulus to initiate scytonemin biosynthesis, Δ1278 was incapable of producing scytonemin. A phenotypic characterization of Δ1278 suggests that, aside from the ability to produce scytonemin, the deletion of Npun_F1278 does not affect the cell morphology, cellular differentiation capability, or lipid-soluble pigment complement of Δ1278 compared to the wild type. The mutant, however, had a slower specific growth rate and the amount of phycocyanin yielded by Δ1278 differed from the wild type. Given the inability of Δ1278 to produce scytonemin, this study demonstrates that the response regulator Npun_F1278 in N. punctiforme is essential for scytonemin biosynthesis. While most of the evaluated effects of this gene appear to be specific for scytonemin, this regulator may also influence the overall health of the cell and specifically, phycobiliprotein synthesis. This is the first study to identify a regulatory gene involved in the biosynthesis of the sunscreen scytonemin and understanding the transcriptional regulation of scytonemin biosynthesis may allow for mass production in future applications.http://opus.ipfw.edu/stu_symp2016/1001/thumbnail.jp