A framework for sequencing the rice genome

Rice is an important food crop and a model plant for other cereal genomes. The Clemson University Genomics Institute framework project, begun two years ago in anticipation of the now ongoing international effort to sequence the rice genome, is nearing completion. Two bacterial artificial chromosome (BAC) libraries have been constructed from the Oryza sativa cultivar Nipponbare. Over 100 000 BAC end sequences have been generated from these libraries and, at a current total of 28 Mbp, represent 6.5% of the total rice genome sequence. This sequence information has allowed us to draw first conclusions about unique and redundant rice genomic sequences. In addition, more than 60 000 clones (19 genome equivalents) have been successfully fingerprinted and assembled into contigs using FPC software. Many of these contigs have been anchored to the rice chromosomes using a variety of techniques. Hybridization experiments have shown these contigs to be very robust. Contig assembly and hybridization experiments have revealed some surprising insights into the organization of the rice genome, which will have significant repercussions for the sequencing effort. Integration of BAC end sequence data with anchored contig information has provided unexpected revelations on sequence organization at the chromosomal level.