Abstract
BackgroundA horizontal gene transfer has brought an active nuclear gene, PgiC2, from a polyploid Poa species (P. palustris or a close relative) into the common grass sheep's fescue (Festuca ovina). The donor and the receptor species are strictly reproductively separated, and PgiC2 occurs in a polymorphic state within F. ovina. The active gene copy is normally closely linked to a very similar pseudogene.Methodology/Principal FindingsBy genome walking we have obtained the up- and downstream sequences of PgiC2 and of corresponding genes in the donor and recipient species. Comparisons of these sequences show that the complete upstream region necessary for the gene's expression is included in the transferred segment. About 1 kb upstream of PgiC2 a fragment with transposition associated properties has been found (TAF). It is present in P. palustris and its polyploid relatives, though not at the homologous position, and is absent from many other grasses, including non-transgenic F. ovina plants. It is possible that it is a part of a transposing element involved in getting the gene into a transferring agent and/or into the recipient chromosome.Conclusions/SignificanceThe close similarity of the up- and downstream regions with the corresponding regions in P. palustris excludes all suggestions that PgiC2 is not a HGT but the result of a duplication within the F. ovina lineage. The small size of the genetic material transferred, the complex nature of the PgiC2 locus, and the associated fragment with transposition associated properties suggest that the horizontal transfer occurred via a vector and not via illegitimate pollination.
Highlights
Horizontal gene transfer, HGT, can be defined as transfer of genetic material between distantly related genomes by some mechanism other than sexual fertilization
The PgiC2 locus in F. ovina was originally detected through the presence of too many bands in an isozyme survey [14]
The sequences of PgiC2 and PgiC1 from F. ovina and PgiC from P. palustris are all similar in region I, though PgiC1 becomes increasingly divergent with increasing distance from the gene
Summary
Horizontal gene transfer, HGT, can be defined as transfer of genetic material between distantly related genomes by some mechanism other than sexual fertilization. Using wide crosses in combination with embryo rescue and other laboratory technologies, researchers in plant breeding have succeeded in transferring chromosomes, chromosome arms, or parts of chromosomes between species and/or genera [see, for example, 8]. Whether such processes occur in nature is, uncertain. A horizontal gene transfer has brought an active nuclear gene, PgiC2, from a polyploid Poa species (P. palustris or a close relative) into the common grass sheep’s fescue (Festuca ovina). The active gene copy is normally closely linked to a very similar pseudogene
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