Scientists at the Duke Institute for Genome Sciences and Policy (IGSP) and the University of Basel have unveiled the complete genome sequence of a pathogenic plant fungus that infects agricultural crops, including cotton and citrus fruits in the tropics.

The fungus, Ashbya gossypii, has the smallest genome yet characterized among free-living eukaryotes, which are the single-celled and multi-cellular organisms that include fungi, plants and animals.

The team was led by Fred Dietrich of the Duke IGSP’s Center for Genome Technology and Peter Phillipsen of the University of Basel.

The work was completed with the funding and collaboration of Novartis (now Syngenta) in Research Triangle Park, but the researchers have no financial ties to either company.

Dietrich and Phillipsen reported their findings related to the sequencing of the fungal genome in the March 4 edition of Science Express, the online version of the journal Science.

“We expect many similarities in function among all types of fungal pathogens … whether they infect plants or humans,” said Dietrich, first author of the study. “Understanding one will provide insight into fungal pathogens in general in terms of the forces that drive them.”

Ashbya’s stripped-down genome, containing just 9.2 million DNA base pairs, will further simplify the task of deciphering genes and their functions, he added. The genomes of other important fungal pathogens can include as many as 200 million base pairs, more than 20 times that of the Ashbya genome, while humans have 6 billion DNA base pairs.

The researchers first sequenced the Ashbya genome three times over in many segments and assembled those pieces into the sequences of the fungus’ seven chromosomes. The team then filled in any remaining gaps in the initial scaffold through additional sequencing. By comparing the sequence information to the yeast genome, the investigators identified the location of genes along the chromosomes.

Dietrich says the fully annotated sequence will be made publicly available on GenBank, the National Institutes of Health genetic sequence database.

“This is the culmination of the work of many people over more than 10 years,” he said. “It’s very satisfying to finally be able to make this data public,” since the support of Novartis hinged on an agreement that the data not be made public until the genome was complete.

Duke IGSP www.genomics.duke.edu