|Kema, Gert - PLANT RES. INT. NETHERL|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2007
Publication Date: March 28, 2007
Citation: Goodwin, S.B., Kema, G.H. 2007. Sequencing on the Mycosphaerella branch of the fungal evolutionary tree [abstract]. Abstracts of the 2nd Annual U.S. D.O.E. Joint Genome Institute User Meeting, Walnut Creek, CA. p. 2-3. Technical Abstract: Mycosphaerella and its asexual derivatives comprise the largest group of plant-pathogenic fungi. Many diseases caused by species of Mycosphaerella are economically significant and require huge inputs of fungicides for effective control. Despite these high economic costs, species of Mycosphaerella have been ignored for genomic sequencing until recently. This changed with the completion of the genomic sequence of the Septoria tritici blotch pathogen of wheat, M. graminicola, and of a 7.1x draft sequence of the black Sigatoka pathogen of banana, M. fijiensis. Comparison of these sequences revealed a huge and unexpected difference in genome size, from about 40 Mb for M. graminicola to more than 74 Mb for M. fijiensis. This difference apparently originated in one of the ancestors to a group of Mycosphaerella species attacking banana, and is due to amplification of transposable elements rather than to genome duplications. Some of the transposons appear to be helitrons, which have not been reported previously from ascomycete fungi. Both species seem to have a slightly smaller and possibly more specialized set of cell-wall-degrading enzymes in comparison to other plant-pathogenic fungi with sequenced genomes, which may indicate a mode of pathogenesis that involves stealth rather than brute force. The genomic sequence will provide an unprecedented picture of the genetic changes that occur during the switch from endophytic to pathogenic growth. Enzymes that are required for pathogenicity may indicate new fungicide targets and could be useful for improving ethanol production. The genomic sequences also showed that the closest relatives to Mycosphaerella are fungi in the order Pleosporales, in accordance with classical taxonomy.