Dissection of rye B chromosomes, and nondisjunction properties of the dissected segments in a common wheat background.
The rye B chromosome is a supernumerary chromosome that increases in number in its host by directed postmeiotic drive. Two types of rye B chromosomes that had been introduced into common wheat were dissected into separate segments by the gametocidal system to produce a number of rearranged B chromosomes, such as telosomes, terminal deletions and translocations with wheat chromosomes. A total of 13 dissected B chromosomes were isolated in common wheat, and were investigated for their nondisjunction properties. Rearranged B chromosomes, separated from their B-specific repetitive sequences on the distal part of the long arm, did not undergo nondisjunction, and neither did a translocated wheat chromosome carrying a long-arm distal segment containing the B-specific repetitive sequences. However, such rearranged B chromosomes, missing their B-specific sequences could undergo nondisjunction when they coexisted with the standard B chromosome or a wheat chromosome carrying the B-specific sequences. Deficiencies of the short arm did not completely abolish the nondisjunction properties of the B chromosome, but did reduce the frequency of nondisjunction. These results confirmed previous suggestions that the directed nondisjunction of the rye B chromosome is controlled by two elements, pericentromeric sticking sites and a trans-acting element carried at the distal region of the long arm of the B chromosome. Additionally, it is now shown that the distal region of the long arm of the B chromosome which provides this function is that which carries the B-specific repetitive sequences.
Endo
Takashi Ryu
TR
Graduate School of Agriculture, Kyoto University, Kyoto, Japan. trendo@kais.kyoto-u.ac.jp
Nasuda
Shuhei
S
Jones
Neil
N
Dou
Quanwen
Q
Akahori
Atsushi
A
Wakimoto
Munenori
M
Tanaka
Hiroyuki
H
Niwa
Katsumasa
K
Tsujimoto
Hishashi
H
D032461:Chromosomes, Plant; D020732:Cytogenetic Analysis; D018744:DNA, Plant / Q000378:metabolism; D015321:Gene Rearrangement; D017343:Genes, Plant; D018745:Genome, Plant; D017404:In Situ Hybridization, Fluorescence; D009630:Nondisjunction, Genetic; D020161:Physical Chromosome Mapping; D012434:Secale / Q000235:genetics*; D014908:Triticum / Q000235:genetics*
D018744:DNA, Plant