An 82 bp tandem repeat family typical of 3' non-coding end of Gypsy/TAT LTR retrotransposons is conserved in Coffea spp. pericentromeres.

Abstract

Coffea spp. chromosomes are very small and accumulate a variety of repetitive DNA families around the centromeres. However, the proximal regions of Coffea chromosomes remain poorly understood, especially regarding the nature and organisation of the sequences. Taking advantage of the genome sequences of C. arabica (2n = 44), C. canephora, and C. eugenioides (C. arabica progenitors with 2n = 22) and good coverage genome sequencing of dozens of other wild Coffea spp., repetitive DNA sequences were identified, and the genomes were compared to decipher particularities of pericentromeric structures. The searches revealed a short tandem repeat (82 bp length) typical of Gypsy/TAT LTR retrotransposons, named Coffea_sat11. This repeat organises clusters with fragments of other transposable elements, comprising regions of non-coding RNA production. Cytogenomic analyses showed that Coffea_sat11 extends from the pericentromeres towards the middle of the chromosomal arms. This arrangement was observed in the allotetraploid C. arabica chromosomes, as well as in its progenitors. This study improves our understanding of the role of the Gypsy/TAT LTR retrotransposon lineage in the organisation of Coffea pericentromeres, as well as the conservation of Coffea_sat11 within the genus. The relationships between fragments of other transposable elements and the functional aspects of these sequences on the pericentromere chromatin were also evaluated. Highlights: A scattered short tandem repeat, typical of Gypsy/TAT LTR retrotransposons, associated with several fragments of other transposable elements, accumulates in the pericentromeres of Coffea chromosomes. This arrangement is preserved in all clades of the genus and appears to have a strong regulatory role in the organisation of chromatin around centromeres.