Press Release

March 13 , 2013

Incorporated Administrative Agency, Fisheries Research Agency

Nori genome has been unveiled!

  • The first symbiont-free sequencing of a marine red alga.
  • A compact genome than expected.
  • Novel gene candidates useful for culture.

Nori is an important edible laver in Japan, which is essential for making onigiri (rice balls), makizushi (sushi rolls), and so on. This seaweed, a type of marine red algae, has been cultured in many countries, but the molecular basis of its physiology is poorly understood.

In genomic era, like other organisms, nori has been also a target of whole genome project, thereby we will harvest more information about marine red algae. Actually we have promoted the genome project of susabi-nori (Pyropia yezoensis) for cultural applications, collaborating with Hitachi Solutions, Ltd. and Japan Software Management Co. Ltd. However, the whole genome sequencing of P. yezoensis has been quite difficult until now because of DNA contamination of symbiotic bacteria tightly attaching to the algal cells.

Here, we prepared symbiont-free protoplasts of P. yezoensis, and determined, for the first time, the genome sequence. Collaborating further with the National Institute of Genetics and the Kyushu University, we successfully reconstructed the symbiont-free nuclear genome of susabi-nori, which provides fruitful findings that have never been reported in red algae. The first finding is compactness of the nori genome: the shotgun sequences were assembled into 46,634 contigs totaling 43 megabases, much smaller than ever expected. Second, in the genome, we found novel gene candidates related to the color trait of red algae and symbiosis with bacteria.

These findings can ensure that nori genome will be a model genome of red algae in the near future. Furthermore, we expect that the genomic information obtained here will contribute much to nori culture such as cultivar improvement.


Our work has been published in the journal PLOS ONE on March 12, 2013 (doi: http://dx.plos.org/10.1371/journal.pone.0057122).
The sequence data is available at our web site, http://nrifs.fra.affrc.go.jp/ResearchCenter/5_AG/genomes/nori/.


Thalli of P. yezoensis

Protoplasts of P. yezoensis. The mean diameter is ca. 20 μm.