Ordered YAC Clone Contigs Assigned to Rice Chromosomes 3 and 11

Yeast artificial chromosome (YAC) clones were arranged on the positions of restriction fragment length polymorphism (RFLP) and sequence-tagged site (STS) markers already mapped on the high-resolution genetic maps of rice chromosomes 3 and 11. From a total of 416 and 242 YAC clones selected by colony/Southern hybridization and polymerase chain reaction (PCR) analysis, 238 and 135 YAC clones were located on chromosomes 3 and 11, respectively. For chromosomes 3 and 11, 24 YAC contigs and islands with total coverage of about 46% and 12 contigs and islands with coverage of about 40%, respectively, were assigned. Although many DNA fragments of multiple copy marker sequences could not be mapped to their original locations on the genetic map by Southern hybridization because of a lack of RFLP, the physical mapping of YAC clones could often assign specific locations of such multiple copy sequences on the genome. The information provided here on contig formation and similar sequence distribution revealed by ordering YAC clones will help to unravel the genome organization of rice as well as being useful in isolation of genes by map-based cloning.