Data from: Cyanobacteriochromes from Gloeobacterales provide new insight into the diversification of cyanobacterial photoreceptors

The phytochrome superfamily comprises three groups of photoreceptors sharing a conserved GAF (cGMP-specific phosphodiesterases, cyanobacterial adenylate cyclases, and formate hydrogen lyase transcription activator FhlA) domain that uses a covalently attached linear tetrapyrrole (bilin) chromophore to sense light. Knotted red/far-red phytochromes are widespread in both bacteria and eukaryotes, but cyanobacteria also contain knotless red/far-red phytochromes and cyanobacteriochromes (CBCRs). Unlike phytochromes, CBCRs require only the GAF domain for bilin binding, chromophore ligation, and full, reversible photoconversion. CBCRs can sense a wide range of wavelengths (ca. 330-750 nm) and can regulate phototaxis, second messenger metabolism, and optimization of the cyanobacterial light-harvesting apparatus. However, the origin and diversification of CBCRs are not well understood. In the current work, we use the increasing availability of genomes and metagenome-assembled-genomes from early-branching cyanobacteria to identify the earliest branches in CBCR evolution. Our analyses also show that early-branching cyanobacteria contain more recently evolved CBCRs, implicating significant diversification of CBCRs very early in cyanobacterial evolution. Moreover, we show that early-branching CBCRs behave as integrators of light and pH, providing a potential unique function for early CBCRs that could have led to their retention and subsequent diversification. Our results thus provide new insight into the origins of these diverse cyanobacterial photoreceptors.