[All-postdocs] Bioseminar - Blair Paul

[Ana Velez]

Woods Hole Oceanographic Institution
Biology Department Seminar

Thursday, March 12, 2026 - 12:00 pm
Redfield Auditorium

Blair Paul
Assistant Scientist, Marine Biological Laboratory

Targeted Hypermutation in Multicellular Cyanobacteria
Mutation permeates all of life and is the fundamental source of evolution. Diversity-generating retroelements (DGRs) induce targeted hypermutation of specific genes, maximizing amino acid diversity via codon rewriting. These prodigious engines of protein variation are found in vast lineages of bacteria and archaea, including their viruses, and can accelerate the evolution of specific genes. Yet we currently know little about the cellular functions of DGR targets or the phenotypes that emerge from their diversification. Following our discovery that DGRs are especially common in multicellular cyanobacteria, we found evidence of rampant diversification in wild populations of the marine bacterium Trichodesmium erythraeum. Using a laboratory model of multicellular cyanobacteria, we determined that gene targets mutate at a constant low rate in the absence of exogenous stress or stimuli. To establish a benchmark for DGR expression during the natural diel growth cycle, we conducted a transcriptomic time-series experiment with cultures of Nostoc punctiforme. Our analysis uncovered day-night shifts in central carbon metabolism, repair, and activation of mobile elements, including prophage and transposons. DGR target genes were constitutively expressed throughout the 9-day experiment, with elevated expression during an extended period of darkness. Diversifying machinery, including reverse transcriptase and a putative accessory protein, showed a narrow range of expression, suggesting the DGRs may be under tight host control.  Current and future efforts aim to determine whether phage infection or other molecular signals trigger hypermutation in multicellular cyanobacteria. While the functional significance of DGRs in multicellular bacteria remains to be fully appreciated, their apparent value is underlined by their maintenance in ubiquitous marine and terrestrial cyanobacteria.

Biology Seminar Web Page<https://www.whoi.edu/what-we-do/understand/departments-centers-labs/bio/bio-highlights-events/>

For questions, contact:

Ana Maria Velez
Biology Pre-Award Administrative Associate
Ph: 508-289-2334
[signature_1005462319]

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