Analysis of the small chromosomal Prionium serratum (Cyperid) demonstrates the importance of a reliable method to differentiate between mono- and holocentricity

Abstract

AbstractFor a long time, the Cyperid clade (Thurniceae-Juncaceae-Cyperaceae) was considered as a group of species possessing holocentromeres exclusively. The basal phylogenetic position of Prionium serratum L. f. Drège (Thurniceae) within Cyperids makes this species an important specimen to understand the centromere evolution within this clade. Unlike expected, the chromosomal distribution of the centromere-specific histone H3 (CENH3), alpha-tubulin and different centromere associated post-translational histone modifications (H3S10ph, H3S28ph and H2AT120ph) demonstrate a monocentromeric organisation of P. serratum chromosomes. Analysis of the high-copy repeat composition resulted in the identification of a centromere-localised satellite repeat. Hence, monocentricity was the ancestral condition for the Juncaceae-Cyperaceae-Thurniaceae Cyperid clade and holocentricity in this clade has independently arisen at least twice after differentiation of the three families, once in Juncaceae and the other one in Cyperaceae. Methods suitable for the identification of holocentromeres are discussed.