Plant & Animal Genome VI Conference

W69

A RICE EXPRESSED SEQUENCE TAG MAP

Rice Genome Research Program, National Institute of Agrobiological Resources / Institute of the Society for Techno-innovation of Agriculture, Forestry and Fisheries, Tsukuba, Ibaraki 305, Japan

To obtain all the genetic and molecular information for rice, Oryza sativa, as an array of nucleotides, we first produced about 2300 markers, mainly based on RFLPs spaced every 0.7 cM on average. Then we used them as landmarkers for screening YAC clones from a library of about 7000 clones with an average insert size of 350 kb. By this method, about 70% of the rice genetic map was covered by about 2500 YAC clones with 244 contigs and 269 island YACs. This map serves as a skeleton for making an expressed sequence tag (EST) map of the rice genome. Although about 1500 RFLPs markers among the 2300 genetic markers are rice cDNAs, these cDNAs correspond to only about 5% of the estimated total number of the rice genes. We now have more than 15 thousand independent rice ESTs. The assignment of the YACs from which these ESTs originated can fill the gaps in the skeleton map and make feasible the selection of YACs carrying rice genes homologous to other cereals (synteny analysis). Further, in the future, the localization of ESTs will facilitate the elucidation of sequence rules required for the transcription process. We launched this mapping by using 3-dimensionally pooled YACs as primary templates for PCR with 3'-UTR sequences of target ESTs as primers. The location of each assigned YAC was determined with reference to the YAC skeleton map.