期刊
FUNGAL GENETICS AND BIOLOGY
卷 35, 期 1, 页码 39-51出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1006/fgbi.2001.1309
关键词
Epichloe endophyte; concerted evolution; hybridization; ribosomal RNA; dispersed repeats; homogenization
We examined ribosomal RNA concerted evolution in an Epichloe endophyte interspecific hybrid (Lp1) and its progenitors (Lp5 and E8). We show that the 5S rrn genes are organized as dispersed copies. Cloned 5S gene sequences revealed two subfamilies exhibiting 12% sequence divergence, with substitutions forming co-evolving pairs that maintain secondary structure and presumably function. Observed sequence patterns are not fully consistent with either concerted or classical evolution. The 5S rrn genes are syntenic with the tandemly arranged rDNA genes, despite residing outside the rDNA arrays. We also examined rDNA concerted evolution. Lp1 has rDNA sequence from only one progenitor and contains multiple rDNA arrays. Using 5S rrn genes as chromosomal markers, we propose that interlocus homogenization has replaced all Lp5 rDNA sequence with E8 sequence in the hybrid. This interlocus homogenization appears to have been rapid and efficient and is the first demonstration of hybrid interlocus homogenization in the Fungi. (C) 2002 Elsevier Science (USA).
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