|Budget Amount *help
¥1,700,000 (Direct Cost : ¥1,700,000)
Fiscal Year 1991 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1990 : ¥700,000 (Direct Cost : ¥700,000)
In a common wheat strain with rye cytoplasm, at least one diminutive chromosome, called "midget" always exists. The midget chromosome does not pair with any of the wheat chromosomes at meiosis, and the seeds of this strain without this chromosome are inviable because of their endosperm abortion. These results indicate that the midget chromosome was derived from certain segment(s) of rye chromosome(s), having the gene(s)essential for rye cytoplasmic function. To analyze the gene(s), in this study, we attempted to isolate the midget chromosome-specific DNA sequences by using a genomic subtraction method.
Three different rye-specific sequences were isolated. Dot and Southern blot analyses showed that the inserted sequence of one clone(pScm-6.39)was derived from chromosome 5R of rye, and that clone pScm-6.44 contained a common sequence among rye chromosomes 1R, 2R, 3R, 5R and 7R. The insert of pScm-2.3 was shown to be derived from chloroplast DNA of rye.
The origin and molecular structure of the midget chromosome were studied by using in situ hybridization. In situ hybridization with biotinylated rye genomic DNA as a probe clearly showed that the midget chromosome had originated from certain part(s)of rye chromosome(s). The midget chromosome did not possess sequences similar to wheat rDNA nor to rye telomeric sequence with 350-bp repeat unit. However, another repetitive sequence(120-bp family)of rye was found to occur in one distal end of the midget chromosome. The telomere repeat sequences from Arabidopsis thaliana cross-hybridized to both ends of the midget chromosome as well as wheat chromosomes.