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Transposition of MINE, a composite retrotransposon, in the avirulence gene ACE1 of the rice blast fungus Magnaporthe grisea

Fudal I., Böhnert H.U., Tharreau D., Lebrun M.H.. 2005. Fungal Genetics and Biology, 42 (9) : p. 761-772.

DOI: 10.1016/j.fgb.2005.05.001

The ACE1 avirulence gene allele from the rice blast fungus Magnaporthe grisea was characterized in virulent isolate 2/0/3, revealing the insertion of a 1.9 kb MINE retrotransposon in the last ACE1 exon. MINE is a novel chimeric element composed of a transcribed non-coding sequence of 1.1 kb (WEIRD) fused to a 5'-truncated MGL retrotransposon. MINEs were found in high copy number in M. grisea isolates from rice (68 copies) and as a single copy in isolate CD156 from Eleusine. MINEs vary in size (1.3-6.7 kb) with conserved 5' WEIRD sequences and variable 3' MGL sequences. MGLs fused to WEIRDs correspond to different 5'-truncated MGLs with conserved 3' ends. The organization and diversity of MINEs suggest that these retrotransposons result from independent fusions between WEIRD and 5'-truncated MGLs. Such chimera could be formed during MGL reverse transcription as proposed for human U6-LINE1 chimeric retrotransposons and integrated into M. grisea genome using MGL machinery.

Mots-clés : magnaporthe grisea; oryza; oryza sativa; maladie fongique; résistance génétique; génie génétique; expression des gènes; génome; séquence nucléotidique; adn; transposon

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