Amplification and adaptation of centromeric repeats in polyploid switchgrass species.

Centromeres in most higher eukaryotes are composed of long arrays of satellite repeats from a single satellite repeat family. Why centromeres are dominated by a single satellite repeat and how the satellite repeats originate and evolve are among the most intriguing and long-standing questions in centromere biology. We identified eight satellite repeats in the centromeres of tetraploid switchgrass (Panicum virgatum). Seven repeats showed characteristics associated with classical centromeric repeats with monomeric lengths ranging from 166 to 187 bp. Interestingly, these repeats share an 80-bp DNA motif. We demonstrate that this 80-bp motif may dictate translational and rotational phasing of the centromeric repeats with the cenH3 nucleosomes. The sequence of the last centromeric repeat, Pv156, is identical to the 5S ribosomal RNA genes. We demonstrate that a 5S ribosomal RNA gene array was recruited to be the functional centromere for one of the switchgrass chromosomes. Our findings reveal that certain types of satellite repeats, which are associated with unique sequence features and are composed of monomers in mono-nucleosomal length, are favorable for centromeres. Centromeric repeats may undergo dynamic amplification and adaptation before the centromeres in the same species become dominated by the best adapted satellite repeat.

Yang X ，Zhao H ，Zhang T ，Zeng Z ，Zhang P ，Zhu B ，Han Y ，Braz GT ，Casler MD ，Schmutz J ，Jiang J ... -  《-》

Repeatless and repeat-based centromeres in potato: implications for centromere evolution.

Gong Z ，Wu Y ，Koblízková A ，Torres GA ，Wang K ，Iovene M ，Neumann P ，Zhang W ，Novák P ，Buell CR ，Macas J ，Jiang J ... -  《-》

The formation and evolution of centromeric satellite repeats in Saccharum species.

Centromeres in eukaryotes are composed of tandem DNAs and retrotransposons. However, centromeric repeats exhibit considerable diversity, even among closely related species, and their origin and evolution are largely unknown. We conducted a genome-wide characterization of the centromeric sequences in sugarcane (Saccharum officinarum). Four centromeric tandem repeat sequences, So1, So103, So137 and So119, were isolated. So1 has a monomeric length of 137 bp, typical of a centromeric satellite, and has evolved four variants. However, these So1 variants had distinct centromere distributions and some were unique to an individual centromere. The distributions of the So1 variants were unexpectedly consistent among the Saccharum species that had different basic chromosome numbers or ploidy levels, thus suggesting evolutionary stability for approximately 7 million years in sugarcane. So103, So137 and So119 had unusually longer monomeric lengths that ranged from 327 to 1371 bp and lacked translational phasing on the CENH3 nucleosomes. Moreover, So103, So137 and So119 seemed to be highly similar to retrotransposons, which suggests that they originated from these mobile elements. Notably, all three repeats were flanked by direct repeats, and formed extrachromosomal circular DNAs (eccDNAs). The presence of circular molecules for these retrotransposon-derived centromeric satellites suggests an eccDNA-mediated centromeric satellite formation pathway in sugarcane.

Huang Y ，Ding W ，Zhang M ，Han J ，Jing Y ，Yao W ，Hasterok R ，Wang Z ，Wang K ... -  《-》

The CentO satellite confers translational and rotational phasing on cenH3 nucleosomes in rice centromeres.

Zhang T ，Talbert PB ，Zhang W ，Wu Y ，Yang Z ，Henikoff JG ，Henikoff S ，Jiang J ... -  《-》

Karyotype variation is indicative of subgenomic and ecotypic differentiation in switchgrass.

Young HA ，Sarath G ，Tobias CM 《BMC PLANT BIOLOGY》