Dynamic nucleolar activity in wheat × Aegilops hybrids: evidence of C-genome dominance
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NOR loci of C-subgenome are dominant in wheat × Aegilops interspecific hybrids, which may have evolutionary implications for wheat group genome dynamics and evolution.
After interspecific hybridisation, some genes are often expressed from only one of the progenitor species, shaping subsequent allopolyploid genome evolution processes. A well-known example is nucleolar dominance, i.e. the formation of cell nucleoli from chromosomes of only one parental species. We studied nucleolar organizing regions (NORs) in diploid Aegilops markgrafii (syn: Ae. caudata; CC), Ae. umbellulata (UU), allotetraploids Aegilops cylindrica (CcCcDcDc) and Ae. triuncialis (CtCtUtUt), synthetic interspecific F1 hybrids between these two allotetraploids and bread wheat (Triticum aestivum, AABBDD) and in F3 generation hybrids with genome composition AABBDDCtCtUtUt using silver staining and fluorescence in situ hybridization (FISH). In Ae. markgrafii (CC), NORs of both 1C and 5C or only 5C chromosome pairs were active in different individual cells, while only NORs on 1U chromosomes were active in Ae. umbellulata (UU). Although all 35S rDNA loci of the Ct subgenome (located on 1Ct and 5Ct) were active in Ae. triuncialis, only one pair (occupying either 1Cc or 5Cc) was active in Ae. cylindrica, depending on the genotype studied. These C-genome expression patterns were transmitted to the F1 and F3 generations. Wheat chromosome NOR activity was variable in Ae. triuncialis × T. aestivum F1 seeds, but silenced by the F3 generation. No effect of maternal or paternal cross direction was observed. These results indicate that C-subgenome NOR loci are dominant in wheat × Aegilops interspecific hybrids, which may have evolutionary implications for wheat group genome dynamics and allopolyploid evolution.
KeywordsNucleolar dominance 35S rRNA gene Polyploidization Interspecific hybridization
This research was financially supported by the University of Kurdistan, Sanandaj. The authors declare that they have no competing interests. The first author acquired some data (FISH of Ae. triuncialis and its subgenomes) at Andreas Houben’s lab at IPK, Germany. ASM is supported by DFG Emmy Noether award MA6473/1-1.
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Conflict of interest
The authors declare that they have no competing interests.
The manuscript has not been submitted to more than one journal for simultaneous consideration. No data have been fabricated or manipulated to support our conclusions. We have acknowledged and cited the work of others to the best of our knowledge. All authors read and approved the final manuscript.
- Grummt I, Längst G (2013) Epigenetic control of RNA polymerase I transcription in mammalian cells. BBA-Gene Regul Mech 1829:393–404Google Scholar
- Książczyk T, Kovarik A, Eber F, Huteau V, Khaitova L, Tesarikova Z, Coriton O, Chèvre A-M (2011) Immediate unidirectional epigenetic reprogramming of NORs occurs independently of rDNA rearrangements in synthetic and natural forms of a polyploid species Brassica napus. Chromosoma 120:557–571CrossRefPubMedGoogle Scholar
- Pikaard CS (2001) Nucleolar dominance. Wiley, Encyclopedia of Life SciencesGoogle Scholar
- Reeder RH (1974) Ribosomes from eukaryotes: genetics. In: Nomura M (ed) Ribosomes. Cold Spring Harbor Laboratory Press, New York, pp 489–519Google Scholar
- Soltis DE, Buggs RJ, Doyle JJ, Soltis PS (2010) What we still don’t know about polyploidy. Taxon 59:1387–1403Google Scholar