ARS | Publication request: Comparative repeat analysis of two fungi from the genus Mycosphaerella

Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2007
Publication Date: January 12, 2008
Citation: Dhillon, B., Goodwin, S.B. 2008. Comparative repeat analysis of two fungi from the genus Mycosphaerella. Plant and Animal Genome Conference. Available: http://www.intlpag.org/16/abstracts/pag16_p05a_220.html.

Technical Abstract: Mycosphaerella graminicola (anamorph: Septoria tritici) is an economically important pathogen of wheat in the US, causing septoria tritici blotch disease. The nuclear genome of M. graminicola is 39.7 Mb, and it is currently being sequenced to completion. A closely related fungus from the same genus is Mycosphaerella fijiensis (anamorph: Paracercospora fijiensis), which is a non-grass monocot pathogen and causes black leaf streak disease in banana. Estimated genome size of M. fijiensis is 73.4 Mb – almost twice that of M. graminicola. Corresponding to increased genome size, the repetitive fraction in M. fijiensis is also higher as compared to M. graminicola. Preliminary analysis of de novo repeats identified by RECON, showed that repeat content in M. fijiensis (35.1%) is about three times more than that in M. graminicola (13.9%). Since genome obesity is usually attributed to the increase in number of Long Terminal Repeat (LTR) retrotransposons, a preliminary analysis of LTR retrotransposons was done in M. graminicola. Initially, LTR_STRUC was used, which identified a total of 41 full-length LTR retrotransposon elements. Structural features (LTR, RT domain, PBS, PPT) from these were then used to search for more elements in M. graminicola. Besides full-length, truncated and nested LTR retrotransposons, we also found several soloLTRs. Further characterization and annotation of LTR elements from M. graminicola is being done. Similar analysis will be done for M. fijiensis. Comparison of repeats from M. graminicola and M. fijiensis could give us clues about the putative role of these repetitive elements in causing genome size expansion in M. fijiensis.