Polycistronic Gene Expression Is Widespread in Green Algae

Single mRNA found to encode more than one protein in seven different algal species, indicating phenomenon conserved in algae for over 700 million years.

The Science

This research at the University of California–Los Angeles aims to iImprove our understanding of gene organization and transcriptional regulation in green algae. Team members used multiple genome-wide gene expression analyses, including full-length transcriptomics (Iso-Seq), chromatin immunoprecipitation, polyadenylation mapping, co-expression analysis, and proteomics were used to determine the presence and expression of polycistronic transcripts in Chlamydomonas and Chromochloris.

The Impact

The dDiscovery of this phenomenon—that two, three, or more proteins could be encoded in one messenger RNA—was validated by genome-wide comparison with five other algae and by expressing synthetic polycistronic gene pairs. Polycistronic transcription was found in seven diverse chlorophyte species, indicating that this phenomenon has been conserved in algae for over 700 million years.


Synthetic polycistronic transcripts containing markers or reporters were successfully expressed in vivo. The relative expression of each gene in a polycistronic transcript can be tuned, demonstrating its applicability for synthetic biology.

Principal Investigator(s)

Sabeeha S. Merchant
University of California–Berkeley


This research was supported by the Office of Biological and Environmental Research, within the U.S. Department of Energy (DOE) Office of Science, Awards DE-SC0018301 for Chromochloris zofingiensis and DE-FC02-02ER63421 for Chlamydomonas reinhardtii. Proteomics analyses were performed under the Facilities Integrating Collaborations for User Science (FICUS) Program Proposals 49262, 49840, 49960, and 50797 and used resources at the DOE Joint Genome Institute (JGI) and the DOE Environmental Molecular Sciences Laboratory (EMSL; grid.436923.9), which are DOE Office of Science user facilities. The work conducted by DOE JGI is supported by DOE Office of Science Contract DE-AC02-05CH11231. The work conducted by EMSL is supported by DOE Office of Science Contract DE-AC05-76RL01830. In vitro translation analysis was supported in part by the DOE Office of Basic Energy Sciences Award DE-SC0017035.


Gallaher, S.D. et al. “Widespread Polycistronic Gene Expression in Green Algae.” Proceedings of the National Academy of Sciences USA 118(7), e2017714118 (2021). [DOI:10.1073/pnas.2017714118]