Novel Orange Carotenoid Proteins Shedding Light on Evolution of Cyanobacteria Photoprotection

blue-green algae
Filamentous blue-green algae [Courtesy Landcare Research. Reused under a Creative Commons license (CC By 4.0, https://creativecommons.org/licenses/by/4.0/).]
A research study has identified and characterized a new, functionally distinct member of the orange carotenoid protein (OCP) family. The OCP complex enables chromatically acclimating blue-green algae to avoid cellular damage and growth inhibition in conditions of high light or nutrient stress. In a recent bioinformatic analysis of all available cyanobacterial genomes, the group found that many of these ecophysiologically diverse organisms encode more than one copy of the full-length OCP. The study’s focus was the filamentous blue-green algae Tolypothrix, which encodes two OCPs.

One copy was determined to be functionally equivalent to the well-characterized OCP of Synechocystis cyanobacteria, dubbed OCP1. But the second, OCP2, was distinct in several key aspects. The researchers hypothesize that OCP2 and another bioinformatically identified protein, OCPx, reflect intermediate stages in the evolution of photoprotection in cyanobacteria.

Bao, H., et al. “Additional Families of Orange Carotenoid Proteins in the Photoprotective System of Cyanobacteria.” Nature Plants 3, Article 17089 (2017). [DOI:10.1038/nplants.2017.89].

Instruments and Facilities: X-ray macromolecular crystallography and diffraction at Advanced Light Source at Lawrence Berkeley National Laboratory.