Structural composition and evolution of jujube centromere reveal a dominant role for LTR retrotransposon

Centromeres are essential for centromere-specific histone H3 (CENH3) recruitment and kinetochore assembly, ensuring accurate chromosome segregation and maintaining genome stability in plants. Although extensively studied in model species, the structural organization of centromeres in nonmodel plants, such as fruit trees, remains poorly explored. Our previous study revealed that jujube centromeres lack the typical tandem repeat (TR)-rich structure, complicating their precise identification. In this study, we updated the genome assembly of jujube (<i>Ziziphus jujuba</i> Mill. 'Dongzao') to a haplotype-resolved T2T version, enabling accurate mapping and comparison of centromeres between haplotypes using CENH3 ChIP-seq. These centromeres, ranging from 0.75 to 1.40 Mb, are largely conserved between haplotypes, except for a localized inversion on chromosome 10. Unlike the TR-rich centromeres found in many plant species, jujube centromeres are predominantly composed of <i>Gypsy</i>-type long-terminal repeat retrotransposons (LTR-RTs). Among these, we identified a centromere-enriched LTR family, centromeric retrotransposons of jujube (CRJ), which is particularly abundant in terminal LTRs compared to the internal transposon regions. Comparative analysis across plant species revealed that centromeric retrotransposons primarily fall into three subfamilies-<i>CRM</i>, <i>Tekay</i>, and <i>Athila</i>-highlighting strong subfamily specificity. Notably, early insertions of CRJ-derived LTR segments contributed to the formation of TR-like structures, suggesting a mechanistic link between transposable elements and the evolution of centromeric tandem repeats. This work provides the first in-depth characterization of a TE-dominated centromere architecture in a fruit tree, offering new insights into the diversity and evolution of plant centromeres.