Gene Conversion and Positive Selection Driving the Evolution of the <Emphasis Type="Italic">Caenorhabditis</Emphasis> ssp. ZIM/HIM-8 Protein Family |
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Authors: | Qingpo Liu |
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Institution: | (1) School of Agriculture and Food Science, Zhejiang Forestry University, Lin’an 311300, Hangzhou, People’s Republic of China |
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Abstract: | In C. elegans, four C2H2 zinc-finger proteins (ZIM-1, ZIM-2, ZIM-3, and HIM-8), which are arranged in tandem, mediate chromosome-specific
pairing and synapsis during meiosis. The zim/him-8 genes from three Caenorhabditis species were contrasted in an effort to investigate the mechanisms driving their evolution. Here it is shown that the preservation
of higher degree of sequence similarity in the N-terminal portion, particularly in several regions within the second exon
between paralogous zim genes (especially between zim-1 and zim-3), is due to independent interparalogue gene conversions. However, the evolutionary force is not uniformly strong across species.
The present data reveal that more frequent gene conversion events have occurred in C. elegans, whereas only gene conversions between zim-1 and zim-3 are detected in C. remanei. Although gene conversions are predicted to be present among zim-1, zim-2, and zim-3 in C. briggsae, the conversion tracts between zim-1/zim-2 and zim-2/zim-3 are very short. Moreover, positive selection analysis was performed on the basis of the significantly discordant phylogenies
reconstructed using the N- and C-terminal sequences, respectively. Several codon sites located in the regions that are supposed
not to have experienced gene conversions are predicted to be under the influence of positive selection. In comparison, stronger
positive selection has acted on the C-terminal region relative to the N-terminal region. Thus, the zim/him-8 genes that evolve concertedly have also been shown to undergo adaptive diversifying selection.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Gene conversion Positive selection Evolution Zinc finger Nematode |
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