Distinct patterns of satDNA distribution in holocentric chromosomes of spike-sedges (<i>Eleocharis</i>, Cyperaceae)

<i>Eleocharis</i> R. Br. (Cyperaceae) species are known for having holocentric chromosomes, which enable rapid karyotype differentiation. High intra- and interspecific variations in chromosome numbers and genome sizes are documented for different <i>Eleocharis</i> species, frequently accompanied by fluctuations in the repetitive DNA fraction. However, a lack of detailed analysis has hampered a better understanding of the interplay between holocentricity and repetitive DNA evolution in this genus. In our study, we confirmed the holocentricity of <i>Eleocharis</i> chromosomes by immunostaining against the kinetochore protein KNL1 and the cell-cycle dependent posttranslational modifications histone H2AThr121ph and H3S10ph. We further studied the composition and chromosomal distribution of the main satellite DNA repeats found in the newly sequenced species <i>Eleocharis maculosa, Eleocharis</i> <i>geniculata, Eleocharis parodii, Eleocharis elegans</i>, and <i>Eleocharis</i> <i>montana</i>. Five of the six satellites discovered were arranged in clusters, while EmaSAT14 was distributed irregularly along the chromatid length in a line-like manner. EmaSAT14 monomers were present in a few copies in few species across the <i>Eleocharis</i> phylogenetic tree. Nonetheless, they were accumulated within a restricted group of Maculosae series, subgenus <i>Eleocharis</i>. The data indicates that the amplification and line-like distribution of EmaSAT14 along chromatids may have occurred recently within a section of the genus.