title: Wheat hybridization and polyploidization results in deregulation of small RNAs.
abstract: Speciation via interspecific or intergeneric hybridization and polyploidization triggers genomic responses involving genetic and epigenetic alterations. Such modifications may be induced by small RNAs, which affect key cellular processes, including gene expression, chromatin structure, cytosine methylation and transposable element (TE) activity. To date, the role of small RNAs in the context of wide hybridization and polyploidization has received little attention. In this work, we performed high-throughput sequencing of small RNAs of parental, intergeneric hybrid, and allopolyploid plants that mimic the genomic changes occurring during bread wheat speciation. We found that the percentage of small RNAs corresponding to miRNAs increased with ploidy level, while the percentage of siRNAs corresponding to TEs decreased. The abundance of most miRNA species was similar to midparent values in the hybrid, with some deviations, as seen in overrepresentation of miR168, in the allopolyploid. In contrast, the number of siRNAs corresponding to TEs strongly decreased upon allopolyploidization, but not upon hybridization. The reduction in corresponding siRNAs, together with decreased CpG methylation, as shown here for the Veju element, represent hallmarks of TE activation. TE-siRNA downregulation in the allopolyploid may contribute to genome destabilization at the initial stages of speciation. This phenomenon is reminiscent of hybrid dysgenesis in Drosophila.
authors.affiliation: Department of Plant Sciences, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Michal
authors.initials: M
authors.lastname: Kenan-Eichler
authors.forename: Dena
authors.initials: D
authors.lastname: Leshkowitz
authors.forename: Lior
authors.initials: L
authors.lastname: Tal
authors.forename: Elad
authors.initials: E
authors.lastname: Noor
authors.forename: Cathy
authors.initials: C
authors.lastname: Melamed-Bessudo
authors.forename: Moshe
authors.initials: M
authors.lastname: Feldman
authors.forename: Avraham A
authors.initials: AA
authors.lastname: Levy
mesh_terms: D015152:Blotting, Northern; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant / Q000235:genetics; D006824:Hybridization, Genetic; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D011123:Polyploidy; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014908:Triticum / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D018744:DNA, Plant; D035683:MicroRNAs; D018749:RNA, Plant; D034741:RNA, Small Interfering