FISH mapping and molecular organization of the major repetitive sequences of tomato.
This paper presents a bird's-eye view of the major repeats and chromatin types of tomato. Using fluorescence in-situ hybridization (FISH) with Cot-1, Cot-10 and Cot-100 DNA as probes we mapped repetitive sequences of different complexity on pachytene complements. Cot-100 was found to cover all heterochromatin regions, and could be used to identify repeat-rich clones in BAC filter hybridization. Next we established the chromosomal locations of the tandem and dispersed repeats with respect to euchromatin, nucleolar organizer regions (NORs), heterochromatin, and centromeres. The tomato genomic repeats TGRII and TGRIII appeared to be major components of the pericentromeres, whereas the newly discovered TGRIV repeat was found mainly in the structural centromeres. The highly methylated NOR of chromosome 2 is rich in [GACA](4), a microsatellite that also forms part of the pericentromeres, together with [GA](8), [GATA](4) and Ty1-copia. Based on the morphology of pachytene chromosomes and the distribution of repeats studied so far, we now propose six different chromatin classes for tomato: (1) euchromatin, (2) chromomeres, (3) distal heterochromatin and interstitial heterochromatic knobs, (4) pericentromere heterochromatin, (5) functional centromere heterochromatin and (6) nucleolar organizer region.
Chang
Song-Bin
SB
Wageningen University, Laboratory of Genetics, 6703 BD, Wageningen, The Netherlands.
Yang
Tae-Jin
TJ
Datema
Erwin
E
van Vugt
Joke
J
Vosman
Ben
B
Kuipers
Anja
A
Meznikova
Marie
M
Szinay
Dóra
D
Lankhorst
René Klein
RK
Jacobsen
Evert
E
de Jong
Hans
H
D002874:Chromosome Mapping / Q000379:methods*; D018744:DNA, Plant / Q000235:genetics*; D018745:Genome, Plant; D006570:Heterochromatin; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D018551:Solanum lycopersicum / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*
D018744:DNA, Plant; D006570:Heterochromatin