Plant Cell 32: 650-665.
Abstract
Centromere position may change despite conserved chromosomal collinearity. Centromere repositioning and evolutionary new centromeres (ENC) were frequently encountered during vertebrate genome evolution, but only rarely observed in plants. The largest crucifer tribe Arabideae (c. 550 species; Brassicaceae, the mustard family) diversified into several well-defined subclades in the virtual absence of chromosome number variation. BAC-based comparative chromosome painting uncovered a constancy of genome structures among 10 analyzed genomes representing seven Arabideae subclades classified as four genera (Arabis, Aubrieta, Draba and Pseudoturritis). Interestingly, the intra-tribal diversification was marked by the high frequency of ENCs on five out of the eight homeologous chromosomes in the crown-group genera, but not in the most ancestral Pseudoturritis genome. From the 32 documented ENCs, at least 26 originated independently including four ENCs recurrently formed at the same position in not closely related species. While chromosomal localization of ENCs does not reflect the phylogenetic position of the Arabideae subclades, centromere seeding was usually confined to long chromosome arms, transforming acrocentric chromosomes to (sub)metacentric ones. Centromere repositioning is proposed as the key mechanism differentiating overall conserved homeologous chromosomes across the crown-group Arabideae subclades. The evolutionary significance of centromere repositioning is discussed in the context of possible adaptive effects on recombination and epigenetic regulation of gene expression.
