Limits...
Genomic change, retrotransposon mobilization and extensive cytosine methylation alteration in Brassica napus introgressions from two intertribal hybridizations.

Zhang X, Ge X, Shao Y, Sun G, Li Z - PLoS ONE (2013)

Bottom Line: The new and absent SSAP bands appeared for 9 out of 11 retrotransposons analyzed, with low frequency of new bands and their total percentage of about 5% in both sets.MSAP analysis indicated that methylation changes were common in these lines (33.4-39.8%) and the hypermethylation was more frequent than hypomethylation.The cryptic mechanism of these changes and potential application of these lines in breeding were also discussed.

View Article: PubMed Central - PubMed

Affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Crop Molecular Breeding Technology, National Center of Oil Crop Improvement (Wuhan), College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, PR China.

ABSTRACT
Hybridization and introgression represent important means for the transfer and/or de novo origination of traits and play an important role in facilitating speciation and plant breeding. Two sets of introgression lines in Brassica napus L. were previously established by its intertribal hybridizations with two wild species and long-term selection. In this study, the methods of amplified fragment length polymorphisms (AFLP), sequence-specific amplification polymorphism (SSAP) and methylation-sensitive amplified polymorphism (MSAP) were used to determine their genomic change, retrotransposon mobilization and cytosine methylation alteration in these lines. The genomic change revealed by the loss or gain of AFLP bands occurred for ∼10% of the total bands amplified in the two sets of introgressions, while no bands specific for wild species were detected. The new and absent SSAP bands appeared for 9 out of 11 retrotransposons analyzed, with low frequency of new bands and their total percentage of about 5% in both sets. MSAP analysis indicated that methylation changes were common in these lines (33.4-39.8%) and the hypermethylation was more frequent than hypomethylation. Our results suggested that certain extents of genetic and epigenetic alterations were induced by hybridization and alien DNA introgression. The cryptic mechanism of these changes and potential application of these lines in breeding were also discussed.

Show MeSH

Related in: MedlinePlus

Pedigrees of B. napus introgression lines from two crosses with two wild species.AACC: Brassica napus. CaCa: Capsella bursa-pastoris. OO: Orychophragmus violaceus. Ca’: individual chromosome or chromosomal segments from C. bursa-pastoris. Cx: uncertain number of the chromosomes from C genome of B. oleracea. The short line between two crosses indicates the generation involving the hybrid or progeny with the partial B. napus complement and some alien chromosomes or segments from which the introgressions are derived.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3585313&req=5

pone-0056346-g001: Pedigrees of B. napus introgression lines from two crosses with two wild species.AACC: Brassica napus. CaCa: Capsella bursa-pastoris. OO: Orychophragmus violaceus. Ca’: individual chromosome or chromosomal segments from C. bursa-pastoris. Cx: uncertain number of the chromosomes from C genome of B. oleracea. The short line between two crosses indicates the generation involving the hybrid or progeny with the partial B. napus complement and some alien chromosomes or segments from which the introgressions are derived.

Mentions: Interspecific hybridization is also widely used to introgress alien genetic elements from wild species into crops to increase genetic variability or transfer desirable traits. In the crosses involving two distantly related species, hybrids with unexpected chromosomal and genomic compositions are often produced, which resulted from the early elimination of alien fragments or chromsomes of the male parent during the hybrid embryo development, genome rearrangements consecutive to ‘genomic shock’ [8], [19] and diploidization [20], [21]. Such hybrids have female-parent-type phenotypes and chromosome numbers but altered genomic compositions and have been reported in several plants, including coffee [22], rapeseed [21], [23]–[27], rice [28] and sunflower [20]. The intertribal hybrids between Brassica napus L. (2n = 38, AACC) and two other crucifers Orychophragmus violaceus (L.) O.E. Schulz (2n = 24, OO), Capsella bursa-pastoris (L.) Medic (2n = 4x = 32) produced by us turned out to be partial hybrids [25], [29], and stable introgression lines have been established by successive selections [30], [31] (Figure 1). Orychophragmus violaceus was suggested to have a phylogenetic position outside of the tribe Brassiceae[32], [33], and C. bursa-pastoris belongs to the tribe Lepidieae. These lines have the same karyotype as B. napus but with genomic change, and some of their phenotypes are different from B. napus by expressing some traits specific for wild species and novel characters. These introgressions have two obvious attributes: they are derivatives of partial sexual hybrids between very distantly related species, and are the products of long artificial selections, up to 20 generations. Comparison of their genetic and epigenetic components with B. napus parents should reveal the extent of the genomic restructuring of recipient B. napus genomes during the relatively long period of hybridization and introgression, and elucidate the general patterns of genetic and epigenetic alteration and stabilization. Our present results indicated that foreign DNA induced genetic recombination of recipient genomes accompanied with extensive DNA cytosine methylation changes, but the activation of retrotransposons occurred for restricted elements.


Genomic change, retrotransposon mobilization and extensive cytosine methylation alteration in Brassica napus introgressions from two intertribal hybridizations.

Zhang X, Ge X, Shao Y, Sun G, Li Z - PLoS ONE (2013)

Pedigrees of B. napus introgression lines from two crosses with two wild species.AACC: Brassica napus. CaCa: Capsella bursa-pastoris. OO: Orychophragmus violaceus. Ca’: individual chromosome or chromosomal segments from C. bursa-pastoris. Cx: uncertain number of the chromosomes from C genome of B. oleracea. The short line between two crosses indicates the generation involving the hybrid or progeny with the partial B. napus complement and some alien chromosomes or segments from which the introgressions are derived.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585313&req=5

pone-0056346-g001: Pedigrees of B. napus introgression lines from two crosses with two wild species.AACC: Brassica napus. CaCa: Capsella bursa-pastoris. OO: Orychophragmus violaceus. Ca’: individual chromosome or chromosomal segments from C. bursa-pastoris. Cx: uncertain number of the chromosomes from C genome of B. oleracea. The short line between two crosses indicates the generation involving the hybrid or progeny with the partial B. napus complement and some alien chromosomes or segments from which the introgressions are derived.
Mentions: Interspecific hybridization is also widely used to introgress alien genetic elements from wild species into crops to increase genetic variability or transfer desirable traits. In the crosses involving two distantly related species, hybrids with unexpected chromosomal and genomic compositions are often produced, which resulted from the early elimination of alien fragments or chromsomes of the male parent during the hybrid embryo development, genome rearrangements consecutive to ‘genomic shock’ [8], [19] and diploidization [20], [21]. Such hybrids have female-parent-type phenotypes and chromosome numbers but altered genomic compositions and have been reported in several plants, including coffee [22], rapeseed [21], [23]–[27], rice [28] and sunflower [20]. The intertribal hybrids between Brassica napus L. (2n = 38, AACC) and two other crucifers Orychophragmus violaceus (L.) O.E. Schulz (2n = 24, OO), Capsella bursa-pastoris (L.) Medic (2n = 4x = 32) produced by us turned out to be partial hybrids [25], [29], and stable introgression lines have been established by successive selections [30], [31] (Figure 1). Orychophragmus violaceus was suggested to have a phylogenetic position outside of the tribe Brassiceae[32], [33], and C. bursa-pastoris belongs to the tribe Lepidieae. These lines have the same karyotype as B. napus but with genomic change, and some of their phenotypes are different from B. napus by expressing some traits specific for wild species and novel characters. These introgressions have two obvious attributes: they are derivatives of partial sexual hybrids between very distantly related species, and are the products of long artificial selections, up to 20 generations. Comparison of their genetic and epigenetic components with B. napus parents should reveal the extent of the genomic restructuring of recipient B. napus genomes during the relatively long period of hybridization and introgression, and elucidate the general patterns of genetic and epigenetic alteration and stabilization. Our present results indicated that foreign DNA induced genetic recombination of recipient genomes accompanied with extensive DNA cytosine methylation changes, but the activation of retrotransposons occurred for restricted elements.

Bottom Line: The new and absent SSAP bands appeared for 9 out of 11 retrotransposons analyzed, with low frequency of new bands and their total percentage of about 5% in both sets.MSAP analysis indicated that methylation changes were common in these lines (33.4-39.8%) and the hypermethylation was more frequent than hypomethylation.The cryptic mechanism of these changes and potential application of these lines in breeding were also discussed.

View Article: PubMed Central - PubMed

Affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Crop Molecular Breeding Technology, National Center of Oil Crop Improvement (Wuhan), College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, PR China.

ABSTRACT
Hybridization and introgression represent important means for the transfer and/or de novo origination of traits and play an important role in facilitating speciation and plant breeding. Two sets of introgression lines in Brassica napus L. were previously established by its intertribal hybridizations with two wild species and long-term selection. In this study, the methods of amplified fragment length polymorphisms (AFLP), sequence-specific amplification polymorphism (SSAP) and methylation-sensitive amplified polymorphism (MSAP) were used to determine their genomic change, retrotransposon mobilization and cytosine methylation alteration in these lines. The genomic change revealed by the loss or gain of AFLP bands occurred for ∼10% of the total bands amplified in the two sets of introgressions, while no bands specific for wild species were detected. The new and absent SSAP bands appeared for 9 out of 11 retrotransposons analyzed, with low frequency of new bands and their total percentage of about 5% in both sets. MSAP analysis indicated that methylation changes were common in these lines (33.4-39.8%) and the hypermethylation was more frequent than hypomethylation. Our results suggested that certain extents of genetic and epigenetic alterations were induced by hybridization and alien DNA introgression. The cryptic mechanism of these changes and potential application of these lines in breeding were also discussed.

Show MeSH
Related in: MedlinePlus