Degenerate MAGGY elements in a subgroup of Pyricularia grisea : a possible example of successful capture of a genetic invader by a fungal genome |
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Authors: | H Nakayashiki N Nishimoto K Ikeda Y Tosa and S Mayama |
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Institution: | (1) Laboratory of Plant Pathology, Faculty of Agriculture, Kobe University, Rokkodai-cho 1-1, Kobe 657-8501, Japan e-mail: hnakaya@kobe-u.ac.jp Tel.: +81-78-803-5867; Fax: +81-78-803-5867, JP |
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Abstract: | The LTR-retrotransposon MAGGY is found sporadically in isolates of Pyricularia grisea (Magnaporthe grisea). Based on a dendrogram constructed by RFLP analysis of rDNA, isolates that carry MAGGY elements were classified into a single
cluster that comprised four rDNA types. However, in a few members of this cluster, exemplified by isolates from common millet
(Panicum miliaceum), the MAGGY element has distinct features. Southern analysis suggested that these isolates possessed a single copy of a MAGGY-related
sequence whose restriction map differed from that of MAGGY itself. Sequence analysis revealed that the MAGGY-related sequence
was a degenerate form of MAGGY, characterized by numerous C:G to T:A transitions, which have often been reported to result
from RIP (Repeat-induced point mutation) or RIP-like processes. However, the favored target site for C:G to T:A transitions
in this fungus, determined by examining a total of 501 sites, was (A/T)pCp(A/T), which differs from that for the RIP process
originally reported in Neurospora (CpA), and from that reported in Aspergillus (CpG). The fact that certain members of the cluster of MAGGY carriers retain a single copy of a degenerate MAGGY element
implies that the ancestor of these isolates successfully “captured” the invading MAGGY element.
Received: 1 February 1999 / Accepted: 8 April 1999 |
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Keywords: | Retrotransposon Filamentous fungi Pyricularia grisea Repeat-induced point mutation (RIP) Gene inactivation |
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