Abstract
Many different processes have an impact on the shape of plant karyotype. Recently, cytogenetic examination of Lolium species has revealed the occurrence of spontaneous fragile sites (FSs) associated with 35S rDNA regions. The FSs are defined as the chromosomal regions that are sensitive to forming gaps or breaks on chromosomes. The shape of karyotype can also be determined by interstitial telomeric sequences (ITSs), what was recognized for the first time in this paper in chromosomes of Festuca pratensis × Lolium perenne hybrids. Both FSs and ITSs can contribute to genome instabilities and chromosome rearrangements. To evaluate whether these cytogenetic phenomena have an impact on karyotype reshuffling observed in Festuca × Lolium hybrids, we examined F1F. pratensis × L. perenne plants and generated F2-F9 progeny by fluorescent in situ hybridization (FISH) using rDNA sequences, telomere and centromere probes, as well as by genomic in situ hybridization (GISH). Analyses using a combination of FISH and GISH revealed that intergenomic rearrangements did not correspond to FSs but overlapped with ITSs for several analyzed genotypes. It suggests that internal telomeric repeats can affect the shape of F. pratensis × L. perenne karyotypes. However, other factors that are involved in rearrangements and have a more crucial impact could exist, but they are still unknown.
Highlights
Cytogenetic analyses, including fluorescent in situ hybridization (FISH) and genomic in situ hybridization (GISH) methods, provide valuable contribution to resolve karyotype variation and evolution (Kopecký et al 2006; Schubert 2007), as well as the genomic composition of hybrids (Zwierzykowski et al.2006, 2008)
We suggest that for synthetic F. pratensis × L. perenne hybrids, interstitial telomeric sequences (ITSs) may have arisen as a result of repairing the DNA breaks or microsatellite expansion
For Festuca × Lolium hybrids, it was previously presented that chromosomes can freely pair and recombine, what is crucial for the production of intergeneric hybrids combining profitable agronomic traits (Zwierzykowski et al 2006, 2011)
Summary
Cytogenetic analyses, including fluorescent in situ hybridization (FISH) and genomic in situ hybridization (GISH) methods, provide valuable contribution to resolve karyotype variation and evolution (Kopecký et al 2006; Schubert 2007), as well as the genomic composition of hybrids (Zwierzykowski et al.2006, 2008). The combination of FISH and GISH techniques has been effectively used for detecting genome compositions and variation in various plant species (Dou et al 2009; Kwiatek et al 2016; Majka et al 2016), including Festuca and Lolium hybrids (Kosmala et al 2006; Książczyk et al 2015). In hybrids of Festuca and Lolium species, interspecies rearrangements have been observed, which are the effects of genomes’ interactions (Zwierzykowski et al.1998, 2011; Kopecký et al 2006)
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