<b>A</b><i><b>TY3/GYPSY</b></i><b>retrotransposon‐like sequence localizes to the centromeric regions of cereal chromosomes</b>

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<jats:title>Summary</jats:title><jats:p><jats:bold>A 745 bp sequence (</jats:bold><jats:italic><jats:bold>pSau3A9</jats:bold></jats:italic><jats:bold>) located at the centromeres of several cereal species was isolated from a sorghum BAC library by</jats:bold><jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#b1"><jats:bold>Jiang</jats:bold><jats:italic><jats:bold>et al</jats:bold></jats:italic><jats:bold>. (1996</jats:bold></jats:ext-link><jats:bold>,</jats:bold><jats:italic><jats:bold>Proc. Natl Acad. Sci. USA</jats:bold></jats:italic><jats:bold>, 93, 14210–14213). We have amplified a partially homologous 809 bp sequence from barley genomic DNA by PCR and localized it to the centromeres of barley, wheat and rye chromosomes by fluorescent</jats:bold><jats:italic><jats:bold>in situ</jats:bold></jats:italic><jats:bold>hybridization (FISH). Sequence analysis showed this barley homolog of</jats:bold><jats:italic><jats:bold>pSau3A9</jats:bold></jats:italic><jats:bold>to have high similarity to the integrase region of the polyprotein gene of</jats:bold><jats:italic><jats:bold>Ty3/gypsy</jats:bold></jats:italic><jats:bold>group retrotransposons. Using this integrase sequence as a probe, several clones were isolated from a lambda library constructed of genomic barley DNA. One of the lambda clones contained coding regions for all five catalytic sites characteristic of the retrotransposon polyprotein. Two direct repeats flanking the polyprotein gene are homologous to the cereal centromeric sequence described by</jats:bold><jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#b2"><jats:bold>Aragón‐Alcaide</jats:bold><jats:italic><jats:bold>et al</jats:bold></jats:italic><jats:bold>. (1996</jats:bold></jats:ext-link><jats:bold>,</jats:bold><jats:italic><jats:bold>Chromosoma</jats:bold></jats:italic><jats:bold>, 105, 261–268) and may represent all or part of the long‐terminal repeats (LTRs). Different plasmid subclones containing various regions of the lambda clone were used in FISH to show that the entire polyprotein gene and upstream flanking sequences, including the presumed LTR, are present at barley centromeres. The preferential (or exclusive) localization of an apparently complete retroelement within the centromeric regions of several cereal species raises interesting questions about its role in karyotype evolution and centromere function.</jats:bold></jats:p>

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