Abstract
Two families of tandem repeats, 180-bp and TR-1, have been found in the knobs of maize. In this study, we isolated 59 clones belonging to the TR-1 family from maize and teosinte. Southern hybridization and sequence analysis revealed that members of this family are composed of three basic sequences, A (67 bp); B (184 bp) or its variants B' (184 bp), 2/3B (115 bp), 2/3B' (115 bp); and C (108 bp), which are arranged in various combinations to produce repeat units that are multiples of approximately 180 bp. The molecular structure of TR-1 elements suggests that: (1) the B component may evolve from the 180-bp knob repeat as a result of mutations during evolution; (2) B' may originate from B through lateral amplification accompanied by base-pair changes; (3) C plus A may be a single sequence that is added to B and B', probably via nonhomologous recombination; and (4) 69 bp at the 3' end of B or B', and the entire sequence of C can be removed from the elements by an unknown mechanism. Sequence comparisons showed partial homologies between TR-1 elements and two centromeric sequences (B repeats) of the supernumerary B chromosome. This result, together with the finding of other investigators that the B repeat is also fragmentarily homologous to the 180-bp repeat, suggests that the B repeat is derived from knob repeats in A chromosomes, which subsequently become structurally modified. Fluorescence in situ hybridization localized the B repeat to the B centromere and the 180-bp and TR-1 repeats to the proximal heterochromatin knob on the B chromosome.
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Claims 9
Claim · model-written summary
TR-1 family members are composed of three basic sequences (A, B or B', 2/3B or 2/3B', C) arranged in combinations that give repeat units of about 180 bp multiples.
Verbatim
e1“members of this family are composed of three basic sequences, A (67 bp); B (184 bp) or its variants B' (184 bp), 2/3B (115 bp), 2/3B' (115 bp); and C (108 bp), which are arranged in various combinations to produce repeat units that are multiples of approximately 180 bp”
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
Claim · model-written summary
The B component may have evolved from the 180-bp knob repeat through mutations during evolution (author interpretation).
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
e3“the B component may evolve from the 180-bp knob repeat as a result of mutations during evolution”
Claim · model-written summary
B' may have originated from B through lateral amplification accompanied by base-pair changes (author interpretation).
- Outcome
- B'e4
- Qualifier
- originate from B through lateral amplification accompanied by base-pair changese4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
e4“B' may originate from B through lateral amplification accompanied by base-pair changes”
Claim · model-written summary
C plus A may be a single sequence added to B and B', probably via nonhomologous recombination (author interpretation).
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
e5“C plus A may be a single sequence that is added to B and B', probably via nonhomologous recombination”
Claim · model-written summary
69 bp at the 3' end of B or B' and the entire sequence of C can be removed from the elements by an unknown mechanism (author interpretation).
- Outcome
- 69 bp at the 3' end of B or B', and the entire sequence of Ce6
- Qualifier
- removed from the elements by an unknown mechanisme6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
e6“69 bp at the 3' end of B or B', and the entire sequence of C can be removed from the elements by an unknown mechanism”
Claim · model-written summary
TR-1 elements show partial sequence homology with two centromeric B-repeat sequences of the supernumerary B chromosome.
- Outcome
- partial homologies between TR-1 elements and two centromeric sequences (B repeats)e7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
e7“Sequence comparisons showed partial homologies between TR-1 elements and two centromeric sequences (B repeats) of the supernumerary B chromosome”
Claim · model-written summary
The B repeat may be derived from knob repeats in A chromosomes, which then became structurally modified (author interpretation).
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
e3“suggests that the B repeat is derived from knob repeats in A chromosomes, which subsequently become structurally modified”
Claim · model-written summary
Fluorescence in situ hybridization localized the B repeat to the B centromere.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
e3“Fluorescence in situ hybridization localized the B repeat to the B centromere”
Claim · model-written summary
Fluorescence in situ hybridization localized the 180-bp and TR-1 repeats to the proximal heterochromatin knob on the B chromosome.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“we isolated 59 clones belonging to the TR-1 family from maize and teosinte”
e3“Fluorescence in situ hybridization localized the B repeat to the B centromere and the 180-bp and TR-1 repeats to the proximal heterochromatin knob on the B chromosome”