Sequencing of telomeres in onion

Plant genus Allium with economically important species like A. cepa and A. sativum (onion and garlic) from monocot order Asparagales used to be classified as a genus with unknown telomeric sequence. Identification of telomeric sequence in large plant genomes with low chromosomal numbers (Allium: 1C=8-80Gb; 2n=14-66) remained challenge for past twenty years. Recently, we have cracked this unusual telomere code in Allium. A combination of well established telomere biology methods and efficiency of next-generation sequencing (NGS) with low genome coverage led to the finding of tandem repeat with CTCGGTTATGGG motif. It was the last missing piece of the puzzle describing telomeric sequence evolution in Asparagales. This evolution started from typical plant motif (TTTAGGG)n – e.g. Doryanthes, going through vertebrate-like (TTAGGG)n – e.g. Ipheion and culminates in divergent tandem repeat (CTCGGTTATGGG)n – Allium. This work was supported by Czech Science Foundation postdoc grant 13-10948P.