Plant & Animal Genomes XIII Conference Plant & Animal Genomes XIII ConferenceJanuary 15-19, 2005
Town & Country Convention Center
San Diego, CA
Hiroshi Mizuno , Shigeki Nakayama , Takashi Matsumoto , Takuji Sasaki
The Rice Genome Research Program (RGP) has constructed physical maps of rice chromosomes 1, 2, 6, 7, 8 and 9 with P1-derived artificial chromosome (PAC) and bacterial artificial chromosome (BAC) clones for genome sequencing. Except for chromosome 1 whose physical size has been previously reported, the remaining five chromosomes were yet to be analyzed for the exact physical length. As of September 2004, the physical maps of these chromosomes comprised 1423 PAC/BAC clones with 18 physical gaps. In this study we have determined the size of these gaps by fluorescence in situ hybridization on extended DNA fibers (fiber-FISH). In order to measure the gap size between adjacent contigs, two flanking PAC/BAC clones with known insert sizes were labeled and hybridized on the extended DNA fibers. At the telomere regions, one PAC/BAC clone localized to the most distal end of each chromosome and the telomere repeat (TTTAGGG)n were used as probes. As a result, the following gap sizes were confirmed:0.8 Mb in chr. 2, 1.0 Mb in chr. 6, 0.7 Mb in chr. 7, 0.2 Mb in chr. 8 and 0.9 Mb in chr. 9. These results together with the nucleotide sequence obtained by RGP reveal the exact physical lengths of these chromosomes for the first time, and that 97.8% (36.0/36.8 Mb) of chr.2, 96.8% (30.7/31.7 Mb) of chr.6, 97.7% (29.6/30.3 Mb) of chr.7, 99.3% (28.4/28.6 Mb) of chr.8, and 96.2% (22.7/23.6 Mb) of chr.9 except for the NOR have been sequenced and indicate that we have almost completed sequencing.