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Title: Genetic and epigenetic changes in somatic hybrid introgression lines between wheat and tall wheatgrass

Author
item LIU, SHUWEI - Shandong University
item LI, FEI - Shandong University
item KONG, LINA - Shandong University
item SUN, YANG - Shandong University
item QIN, LUMIN - Shandong University
item CHEN, SUIYUN - Shandong University
item CUI, HAIFENG - Shandong University
item Huang, Yinghua
item XIA, GUANGMIN - Shandong University

Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2015
Publication Date: 4/1/2015
Citation: Liu, S., Li, F., Kong, L., Sun, Y., Qin, L., Chen, S., Cui, H., Huang, Y., Xia, G. 2015. Genetic and epigenetic changes in somatic hybrid introgression lines between wheat and tall wheatgrass. Genetics. 199(4):1035-1045.

Interpretive Summary: With the world's population continuing to increase, achieving a sustainable food production represents an ever-growing challenge. Plant breeding has resulted in narrowed the genetic base in many crop species, but as yet has had little impact on the genetic diversity present in their wild relatives. In principle, this diversity can be introgressed into crops via sexual hybridization and subsequent backcrossing. To explore this principle, we generated a set of introgression lines displaying a variety of genetic and epigenetic changes relative to their parents using somatic hybridization between wheat and tall wheatgrass, which mimics many of the genetic alterations induced by polyploidization or sexual wide hybridization, in a remarkably short time frame and with stronger extent. The results of this study suggest the somatic hybridization approach not only provides an effective and time efficient means of achieving introgression into a crop species from its wild relatives, but also provides a means to explore the nature of the genetic and epigenetic events induced by 'somatic genomic shock'. This research contributes a better understanding of the underlying mechanisms, which may shed light on the variation released in sexual wild hybrids that has been broadly described as being due to genomic shock.

Technical Abstract: Broad phenotypic variations were induced in derivatives of an asymmetric somatic hybridization of bread wheat (Triticum aestivum) and tall wheatgrass (Thinopyrum ponticum Podp); however, how did these variations happened was unknown. We explored the nature of these variations by cytogenetic assays and DNA profiling techniques to characterize six genetically stable somatic introgression lines. Karyotyping results show the six lines similar to their wheat parent, but GISH analysis identified the presence of a number of short introgressed tall wheatgrass chromatin segments. DNA profiling revealed many genetic and epigenetic differences, including sequences deletions, altered regulation of gene expression, changed patterns of cytosine methylation and the reactivation of retrotransposons. Phenotypic variations appear to result from altered repetitive sequences combined with the epigenetic regulation of gene expression and/or retrotransposon transposition. The extent of genetic and epigenetic variation due to the maintenance of parent wheat cells in tissue culture was assessed and shown to be considerably lower than had been induced in the introgression lines. Asymmetric somatic hybridization provides appropriate material to explore the nature of the genetic and epigenetic variations induced by genomic shock.