Haptophytes are recognized as seminal players in aquatic ecosystem function. These algae are important in global carbon sequestration, form destructive harmful blooms, and given their rich fatty acid content, serve as a highly nutritive food source to a broad range of eco-cohorts. Haptophyte dominance in both fresh and marine waters is supported by the mixotrophic nature of many taxa. Despite their importance the nuclear genome sequence of only one haptophyte, Emiliania huxleyi (Isochrysidales), is available. Here we report the draft genome sequence of Chrysochromulina tobin (Prymnesiales), and transcriptome data collected at seven time points over a 24-hour light/dark cycle.

—Hovde et al.

Chrysochromulina tobin thrives in oceans across the globe. The researchers spent years on a series of experiments to sequence all of Chrysochromulina‘s genes and understand how this alga turns different genes on and off throughout the day. In the process, they discovered that Chrysochromulina would make an ideal subject for investigating how algae make fat, a process important for nutrition, ecology and biofuel production.

It turns out that their fat content gets high during the day and goes down during the night. A very simple pattern, and ideal for follow-up. Algae recently became more familiar to the general populace because of biofuel production. We needed a simple alga for looking at fat production and fat regulation.

—senior author and UW biology professor Rose Ann Cattolico

Like other algae and plants, Chrysochromulina uses light to make food. But they also found another gene, called xanthorhodopsin, that may let the alga harvest light and do work outside of the traditional photosynthetic pathway. Cattolico does not know how the alga uses this gene, but would like to investigate this in the future.

In addition, the team identified numerous genes that appear to harbor antibiotic activity, which may be useful as the need for new antibiotics continues to rise. But Chrysochromulina is not universally against bacteria. Through this project, Cattolico and her team discovered that there are at least 10 bacterial species that appear to enjoy living near Chrysochromulina.

Resources

• Blake T. Hovde, Chloe R. Deodato, Heather M. Hunsperger, Scott A. Ryken, Will Yost, Ramesh K. Jha, Johnathan Patterson, Raymond J. Monnat Jr., Steven B. Barlow, Shawn R. Starkenburg, Rose Ann Cattolico (2015) “Genome Sequence and Transcriptome Analyses of Chrysochromulina tobin: Metabolic Tools for Enhanced Algal Fitness in the Prominent Order Prymnesiales (Haptophyceae)” PLoS Genet 11(9): e1005469 doi: 10.1371/journal.pgen.1005469