Genome differentiation in Aegilops. 1. Distribution of highly repetitive DNA sequences on chromosomes of diploid species

Abstract

Genome differentiation in 12 diploid Aegilops species was analyzed using in situ hybridization with the highly repetitive DNA sequences pSc119 and pAs1 and C-banding. Chromosomes of all these diploid Aegilops species hybridized with the pSc119 probe; however, the level of hybridization and labeling patterns differed among genomes. Only four species (Ae. squarrosa, Ae. comosa, Ae. heldreichii, and Ae. uniaristata) showed distinct hybridization with pAs1. The labeling patterns were species-specific and chromosome-specific. Differences in in situ hybridization (ISH) patterns, also observed by C-banding, exist between the karyotypes of Ae. comosa and Ae. heldreichii, suggesting that they are separate, although closely related, subspecies. The S genome of Ae. spelioides was most similar to the B and G genomes of polyploid wheats on the basis of both C-banding and ISH patterns, but was different from other species of section Sitopsis. These species had different C-banding patterns but they were similar to each other and to Ae. mutica in the distribution of pSc119 hybridization sites. Two types of labeling were detected in Ae. squarrosa with the pAs1 probe. The first resembled that of the D-genome chromosomes of bread wheat, Triticum aestivum L. em. Thell., while the second was similar to the D genome of some of the polyploid Aegilops species. Relationships among diploid Aegilops species and the possible mechanisms of genome differentiation are discussed. Key words : wheat, Triticum, Aegilops, in situ hybridization, C-banding, evolution.

Rapid and Repeatable Elimination of a Parental Genome-Specific DNA Repeat (pGc1R-1a) in Newly Synthesized Wheat Allopolyploids

“…bicornis (Zhang et al 2002). Interestingly, although multiple T. turgidum (genomes AABB), and hexaploid wheat, T. aestivum (genomes AABBDD) (Gill and Apples 1987;Kerby et al 1988;Dvorak and Zhang 1990;Jiang and Gill 1994;Badaeva et al 1996;Daud and Gustafson 1996;Sasanuma et al 1998;Wang et al 2000), pGc1R-1a hybridizes to neither of the polyploid species (Friebe et al 2000;Zhang et al 2002; also Figure 1i). On the basis of this finding, it was suggested that this element was likely eliminated during and/or following the allopolyploidization event leading to speciation of the tetraploid wheat, T. turgidum (Zhang et al 2002).…”

Patterns of heterochromatin distribution in plant chromosomes

“…Therefore, it is important to separately evaluate the distribution of each HC type by cyto-molecular techniques, as has been done for rye (Appels et al, 1978), Scilla (Deumling and Greilhuber, 1982), barley (Brandes et al, 1995), Aegilops (Badaeva et al, 1996) and a few other organisms. Working with conventional cytological techniques, only the HC associated with the nucleolar organizer region (NOR-HC) can be specifically identified, due to secondary constrictions or by silver nitrate impregnation.…”

“…Analyses in several organisms with in situ hybridization of specific satellite DNA fractions have shown that such repeats usually have equilocal distribution (Appels et al, 1978;Badaeva et al, 1996;Brandes et al, 1995). In Aegilops, for instance, a specific satellite sequence was observed in the terminal and subterminal regions of all species investigated, as well as in other chromosomal regions (Badaeva et al, 1996). In some species, two or more unrelated satellite DNAs have been observed occupying the same equilocal sites (Brandes et al, 1995), which may explain those sites that stain positively with different base specific fluorochromes.…”

Molecular-cytogenetic analysis of triticale and wheat lines with introgressions of the tribe Triticeae species genetic material

“…speltoides speltoides. Одновременная гибридиза-ция с зондом pSc119.2 позволяет идентифицировать ин-дивидуальные хромосомы пшеницы и эгилопса (Badaeva et al, 1996;Schneider et al, 2003). На основании данных F��SH и после их сравнения с результатами, получен-ными для родительских форм, установлено, что линия 24-5 несет терминальную транслокацию от Ae.…”