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. 2017 Aug 3;11(3):495-509.
doi: 10.3897/CompCytogen.v11i3.13124. eCollection 2017.

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

Yan Zhao  1   2   3 , Jihong Xie  4 , Quanwen Dou  5 , Junjie Wang  1   2   3 , Zhong Zhang  1   2   3
Affiliations

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

Yan Zhao et al. Comp Cytogenet. .

Abstract

The genomes of five Agropyron Gaertner, 1770 species were characterized using all potential di- or trinucleotide simple sequence repeat (SSR) motifs and four satellite DNA repeats as fluorescence in situ hybridization (FISH) probes. The sites of 5S and 45S rDNA were relatively conserved among the diploid and tetraploid species. A number of sites for the dinucleotide SSRs AC, AG, and pSc119.2 was detected in all investigated species except A. mongolicum Keng, 1938. Several different trinucleotide SSRs were identified in different tetraploid species. All Agropyron species were suggested to include the basic P genome, although genome differentiation was still observed. The P genome of A. mongolicum was distinct from that of the diploid A. cristatum (Linnaeus, 1753) Gaertner, 1770. and other tetraploid species, with no hybridizations for AC, AG, or pSc119.2 observed. This finding supports designation of the P genomes of A. cristatum and A. mongolicum as Pc and Pm, respectively. An exceptional 5S rDNA site revealed in one set of homoeologous chromosomes strongly supports the allopolyploid origin of A. desertorum (Fischer ex Link, 1821) Schultes, 1824. However, the diploid donors to A. desertorum need further investigation. Similarly, the unique FISH pattern of a pair of 5S rDNA-carrying chromosomes was indicative of a potential allopolyploid origin for A. fragile (Roth, 1800) Candargy, 1984. The conserved distribution of 5S and 45S rDNA suggests A. cristatum (4x) and A. michnoi Roshevitz, 1929 are closely related. Two forms of B chromosomes were identified among individuals A. mongolicum and A. desertorum plants.

Keywords: Agropyron; FISH; P genome; rDNA; repetitive sequence.

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Figures

Figure 1.
Figure 1.
FISH patterns of mitotic metaphase chromosomes detected using pAs1 probes (red) combined with 5S rDNA, 45S rDNA, and pSc119.2 probes in A. mongolicum (a–c); 5S rDNA, 45S rDNA, pSc119.2, AG, and AC in A. cristatum (2x) (d–h); 5S rDNA, 45S rDNA, pSc119.2, AAG, ACG, AGG, CAG, CAT, AG, and AC in A. cristatum (4x) (i–r). The pAs1 signals (red) were removed artificially in all images except in (a, d, i). Arrows indicate the target signals (green). Bar = 10μm.
Figure 2.
Figure 2.
FISH patterns of mitotic metaphase chromosomes detected using pAs1 probes (red) combined with 5S rDNA, 45S rDNA, pSc119.2, AG, and AC probes in A. desertorum (a–e); 5S rDNA, 45S rDNA, pSc119.2, AAG, ACT, AG, and AC in A. fragile (f–l); 5S rDNA, 45S rDNA, pSc119.2, CAT, AC, and AG in A. michnoi (m–r). The pAs1 signals (red) were removed artificially in all pictures except in (a, f, m). Arrows indicate the target signals (green). Scale bar = 10 μm.
Figure 3.
Figure 3.
Molecular karyotypes of six Agropyron species probed using pAs1 (red) combined with 5S rDNA (green), 45S rDNA (green) or pSc119.2 (green) sequences. The numbers 1 to 7 designate seven different homologous chromosomes, whereas the same number followed by “^” indicates the respective homoeologous chromosomes in each genome of tetraploid species.
Figure 4.
Figure 4.
FISH patterns of B chromosomes detected by pAs1 (red). a submetacentric B chromosomes in A. mongolicum b metacentric B chromosomes in A. desertorum.
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