Identification of parental genomes and genomic organization in Aster microcephalus var. ovatus

Abstract

The karyotype of diploid Aster iinumae is morphologically similar to that of diploid Aster ageratoides var. ageratoides, however, its chromosome size is apparently smaller (S-type chromosomes versus L-type chromosomes, respectively). The hybrid origin of tetraploid Aster microcephalus var. ovatus (LS-type chromosomes) has previously been suggested by cytogenetics and chloroplast DNA (cp DNA) data. The cp DNA phylogeny also implies that the S-type chromosome is apomorphic, which means that genome size reduction occurred on the evolutionary way to A. iinumae. In this study, we have demonstrated that the chromosome size difference does not depend on the intensity of chromosome condensation but on the DNA content. The simultaneous genomic in situ hybridization (GISH) results show the similarity between S-type chromosomes of A. iinumae and A. microcephalus var. ovatus, and between L-type chromosomes of A. ageratoides and A. microcephalus var. ovatus, which provide additional evidence for A. microcephalus var. ovatus being a tetraploid amphidiploid produced by hybridization between S-type chromosomes and L-type chromosomes. The distribution patterns of Ty1-copia-like retrotransposons were similar in L- and S-type chromosomes. The copies of this retrotransposon dispersed uniformly on all chromosomes, and it is not yet apparent how the Ty1-copia-like retrotransposon affects the size difference between them.

Analysis of Meiotic Chromosome Behaviour in Diploid Individuals of Chrysanthemum zawadskii and Related Species (Asteraceae): Evidence for Chromosome Rearrangements

“…However, unlike other diploid species (2nϭ18) such as Aster iinumae and A. ageratoides which have so distinct karyotypes that can be confirmed in a presumed tetraploid hybrid (Matoba et al 2007), the three Chrysanthemum species are characterized by the indistinguisbale and diverse karyotypes (Kim et al 2003).…”

Review Genomic in situ hybridization in plants

“…Using the GISH technique and the genomic DNA of A. iinumae (2n = 18) and A. ageratoides (2n = 18), without blocking DNA, it was possible to confirm that A. microcephalus var. ovatus was a tetraploid amphidiploid formed by the combination of the genomes of these two species (Matoba et al, 2007).…”

Random Amplified Polymorphic DNA (RAPD) Analysis of Three Japanese <i>Aster</i> Species

“…ovatus with the LS-type karyotype is considered to be an amphidiploid derived from hybridization between A. ageratoides with the L-type karyotype and A. iinumae with the S-type karyotype (Ito et al 1995, 1998, Matoba et al 2005, 2007. The S-type karyotype is suggested to be derived from the L-type karyotype by chromosome size changes (Ito et al 1995(Ito et al 1998.…”

“…Additionally, the tetraploidal LS-type karyotype, considered to be an amphidiploid between them, is found in A. microcephalus var. ovatus (Huziwara 1957b, Tara 1977, Matoba et al 2005, 2007 (Fig. 1).…”

“…Consequently, these works indicated that the lengths of the pappus and chromosomes could have been shortened in parallel evolution. (Matoba et al 2005(Matoba et al , 2007. Aster ageratoides has karyotypes consisting of significantly larger chromosomes (L-type karyotype) than those of A. iinumae (S-type karyotype) (Fig.…”