Chromosomal organization of repetitive DNAs in Hordeum bogdanii and H. brevisubulatum (Poaceae)

Abstract

Molecular karyotypes of Hordeum bogdanii Wilensky, 1918 (2n = 14), and Hordeum brevisubulatum Link, 1844 ssp. brevisubulatum (2n = 28), were characterized by physical mapping of several repetitive sequences. A total of 18 repeats, including all possible di- or trinucleotide SSR (simple sequence repeat) motifs and satellite DNAs, such as pAs1, 5S rDNA, 45S rDNA, and pSc119.2, were used as probes for fluorescence in situ hybridization on root-tip metaphase chromosomes. Except for the SSR motifs AG, AT and GC, all the repeats we examined produced detectable hybridization signals on chromosomes of both species. A detailed molecular karyotype of the I genome of Hordeum bogdanii is described for the first time, and each repetitive sequence is physically mapped. A high degree of chromosome variation, including aneuploidy and structural changes, was observed in Hordeum brevisubulatum. Although the distribution of repeats in the chromosomes of Hordeum brevisubulatum is different from that of Hordeum bogdanii, similar patterns between the two species imply that the autopolyploid origin of Hordeum brevisubulatum is from a Hordeum species with an I genome. A comparison of the I genome and the other Hordeum genomes, H, Xa and Xu, shows that colocalization of motifs AAC, ACT and CAT and colocalization of motifs AAG and AGG are characteristic of the I genome. In addition, we discuss the evolutionary significance of repeats in the genome during genome differentiation.

Diversification of the P genome among Agropyron Gaertn. (Poaceae) species detected by FISH

“…In this study, all potential dinucleotide and trinucleotide SSRs and four satellite DNA repeats were used to characterize the P genome of five Agropyron species. Unlike other genomes such as the H, I, A, B, and D genomes in Triticeae (Cuadrado et al 2007; 2008 ; Dou et al 2016 ), which include a number of SSR hybridization signals based on FISH , the P genome in Agropyron harbored only the dinucleotide SSRs AG and AC in all species, except A. mongolicum , and fewer trinucleotide SSRs in the different species.…”

“…All potential dinucleotide and trinucleotide SSRs and four satellite DNA sequences, namely pAs1 ( Rayburn and Gill 1986 ), pSc119.2 ( Bedbrook et al 1980 ), 5S and 45S rDNA, were used to generate DNA probes. The procedure for labeling the above sequences was performed in accordance with the method of Dou et al (2016) .…”

“…The FISH experiments were conducted following the method of Dou et al (2009 ; 2016 ). The images were captured with a Photometrics CoolSNAP CCD camera (Roper Scientific, Trenton, NJ, USA) using a fluorescence microscope (model DM R HC, Leica Microsystems, Wetzlar, Germany) and processed with the Meta imaging system (Universal Imaging Corporation, West Chester, PA, USA).…”

“…Species-level phylogenies across species can be derived from repeat-based comparative FISH karyotyping ( Jiang and Gill 2006 , Heslop-Harrison and Schwarzacher 2011 ). Comparative FISH may allow to detect genome differentiation between closely related species ( Carmona et al 2013 , Dou et al 2016 ).…”

“…The genomes of Triticeae species are large, of which 75% of the genome comprises repetitive sequences ( Flavell et al 1974 , 1977 ). The genome composition in Triticeae species can be characterized using different microsatellite or satellite repetitive sequences via FISH ( Cuadrado et al 2013 ; Dou et al 2016 ). In the present study, comparative FISH was conducted using all potential dinucleotide and trinucleotide simple sequence repeats (SSRs), 5S and 45S ribosomal DNA (rDNA), pSc119.2, and pAs1 repeats on mitotic chromosomes of five Agropyron species.…”