Preferential elimination of repeated DNA sequences from the paternal, Nicotiana tomentosiformis genome donor of a synthetic, allotetraploid tobacco.
Nicotiana tabacum (tobacco, 2n = 4x = 48) is a natural allotetraploid combining two ancestral genomes closely related to modern Nicotiana sylvestris and Nicotiana tomentosiformis. Here we examine the immediate consequences of allopolyploidy on genome evolution using 20 S4-generation plants derived from a single synthetic, S0 plant made by Burk in 1973 (Th37). Using molecular and cytogenetic methods we analysed 14 middle and highly repetitive sequences that together total approximately 4% of the genome. Two repeats related to endogenous geminiviruses (GRD5) and pararetroviruses (NtoEPRV), and two classes of satellite repeats (NTRS, A1/A2) were partially or completely eliminated at variable frequency (25-60%). These sequences are all from the N. tomentosiformis parent. Genomic in situ hybridization revealed additivity in chromosome numbers in two plants (2n = 48), while a third was aneuploid for an N. tomentosiformis-origin chromosome (2n = 49). Two plants had homozygous translocations between chromosomes of the S- and T-genomes. * The data demonstrate that genetic changes in synthetic tobacco were fast, targeted to the paternal N. tomentosiformis-donated genome, and some of the changes showed concordance with changes that presumably occurred during evolution of natural tobacco.
Skalická
K
K
Institute of Biophysics, Academy of Sciences of the Czech Republic, CZ-61265 Brno, Czech Republic.
Lim
K Y
KY
Matyasek
R
R
Matzke
M
M
Leitch
A R
AR
Kovarik
A
A
D005075:Biological Evolution; D003433:Crosses, Genetic; D018744:DNA, Plant / Q000032:analysis / Q000235:genetics*; D004275:DNA, Ribosomal; D004279:DNA, Viral / Q000235:genetics; D018745:Genome, Plant; D020071:Interspersed Repetitive Sequences; D007621:Karyotyping; D010942:Plant Viruses / Q000235:genetics; D011123:Polyploidy; D020080:Tandem Repeat Sequences; D014026:Nicotiana / Q000235:genetics*
D018744:DNA, Plant; D004275:DNA, Ribosomal; D004279:DNA, Viral