Cytologische Untersuchungen an Arten und Artbastarden von Aquilegia

The Aquilegia genome provides insight into adaptive radiation and reveals an extraordinarily polymorphic chromosome with a unique history

“…The chromosome contained a single large 35S repeat cluster proximal to the centromeric region in all three species. Interestingly, the 35S locus in A. formosa was larger than that of the other two species and formed variable bubbles and fold-backs on extended pachytene chromosomes similar to structures previously observed in Aquilegia hybrids ( Linnert, 1961 ) ( Figure 8 , last panels). The 5S rDNA locus was also proximal to the centromere on chromosome four, although slight differences in the number and position of the 5S repeats between species highlight the dynamic nature of this gene cluster.…”

“…The observation that one Aquilegia chromosome is different from the others is not novel; previous cytological work described a single nucleolar chromosome that appeared to be highly heterochromatic ( Linnert, 1961 ). Using fluorescence in situ hybridization (FISH) with rDNA and chromosome four-specific bulked oligo probes ( Han et al, 2015 ), we confirmed that both the 35S and 5S rDNA loci were localized uniquely to chromosome four in two Aquilegia species and S. adoxoides ( Figure 8 ).…”

“…Furthermore, no heteromorphic sex chromosomes have been observed in the Ranunculales ( Westergaard, 1958 ; Ming et al, 2011 ), making this an unlikely hypothesis. It has also been suggested that chromosome four is a fusion of two homeologous chromosomes ( Linnert, 1961 ), as could result from the ancestral whole genome duplication ( Cui et al, 2006 ; Vanneste et al, 2014 ; Tiley et al, 2016 ), however, analysis of synteny blocks shows that this is not the case ( Aköz and Nordborg, 2018 ).…”