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Rapid evolution of parental rDNA in a synthetic tobacco allotetraploid line
Author(s) -
Skalická Kamila,
Lim K. Yoong,
Matyášek Roman,
Koukalová Blažena,
Leitch Andrew R.,
Kovařík Ales
Publication year - 2003
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.90.7.988
Subject(s) - biology , locus (genetics) , genetics , ribosomal dna , concerted evolution , nicotiana tabacum , chromosome , gene , hybrid , genome , botany , phylogenetics
Unidirectional gene conversion of rDNA units has occurred in the evolution of natural tobacco ( Nicotiana tabacum ). In this paper we report the use of the synthetic tobacco line Th37, 4 n ( N. sylvestris × N. tomentosiformis ), to study early rDNA evolution associated with allopolyploidy. At least three classes of newly amplified rDNA unit variants were identified (17/20 plants). Their presence was often accompanied by near‐complete elimination of N. tomentosiformis ‐donated rDNA units (15/20 plants). Novel rDNA units were of N. tomentosiformis ‐type and contained rearranged subrepeats in the intergenic spacer. The maternal N. sylvestris ‐derived units were unchanged, except for some alteration in the ratio of individual gene family members. A cytogenetic analysis revealed rDNA sites on N. sylvestris ‐derived chromosomes S10, S11, and S12 and N. tomentosiformis ‐derived chromosomes T3 and in some cases T4. An rDNA locus does not occur on N. tomentosiformis chromosome 4. The locus on chromosome T4 of some hybrids correlates with the occurrence of the novel units that probably amplified at the locus. Combined with an analysis of tobacco cultivars, the data indicate that an initial burst of rDNA evolution associated with allopolyploidy was followed by a slower process that led towards reduced complexity and a decreased number of rDNA variants.