The impact of genome defense on mobile elements in Microbotryum
Repeat induced point mutation (RIP), a mechanism causing hypermutation of repetitive DNA sequences in fungi, has been described as a ‘genome defense’ which functions to inactivate mobile elements and inhibit their deleterious effects on genome stability. Here we address the interactions between RIP and transposable elements in the Microbotryumviolaceum species complex. Ten strains of M. violaceum, most of which belong to different species of the fungus, were all found to contain intragenomic populations of copia-like retrotransposons. Intragenomic DNA sequence variation among the copia-like elements was analyzed for evidence of RIP. Among species with RIP, there was no significant correlation between the frequency of RIP-induced mutations and inferred transposition rate based on diversity. Two strains of M. violaceum, from two different plant species but belonging to the same fungal lineage, contained copia-like elements with very low diversity, as would result from a high transposition rate, and these were also unique in showing no evidence of the hypermutation patterns indicative of the RIP genome defense. In this species, evidence of RIP was also absent from a Class II helitron-like transposable element. However, unexpectedly the absolute repetitive element load was lower than in other strains.
KeywordsAnther smut Ustilago violacea Helitron Retrotransposons Copy number variation
- Garber ED, Ruddat M (1998) Genetics of Ustilago violacea. XXXIV. Genetic evidence for a transposable element functioning during mitosis and two transposable elements functioning during meiosis. Int J Plant Sci 159:1018–1022Google Scholar
- Josse T, Teysset L, Todeschini A-L, Sidor C, Anxolabéhère D, Ronsseray S (2007) Telomeric trans-silencing: an epigenetic repression combining RNA silencing and heterochromatin formation. PLOS Genet 3(9):e158Google Scholar