Abstract While the number of leaf-specific expressed genes is estimated to be approximately 6,000, an overview of gene diversity and expression patterns in the leaf of oil- seed rape (Brassica napus L.) has not yet been reported. In an effort to understand gene expression patterns and to identify new genes, we generated 754 expressed sequence tags (ESTs) from the leaf of B. napus. By comparing them to public databases, we showed that 204 of the ESTs (27.1%) have sequence homology to known genes, with 52 of them (6.9%) matching to genes not previously studied in B. napus. The most abundant transcripts were found to be involved in photosynthesis and energy metabolism. When compared with maize leaf ESTs and rice leaf ESTs, the pattern of gene expression was different depending on the developmental stages of the leaf. Key words Brassica napus · Leaf · Expressed sequence tags · cDNA Abbreviations EST Expressed sequence tag · dbEST database for expressed sequence tag · BLAST basic local alignment search tools Introduction The generation of expressed sequence tags (ESTs) by sin- gle-run partial sequencing has proven to be a rapid and ef- ficient way of obtaining information on mRNA expression patterns from a wide variety of tissues and cell types (Ad- ams et al. 1995; Kawamoto et al. 1996). Recently, major plant cDNA sequencing projects have been conducted in Arabidopsis, rice, maize, and chinese cabbage (Uchimiya et al. 1992; Shen et al. 1994; Sasaki et al. 1994; Lim et al. 1996; Delseny et al. 1997). In plants, the number of genes expressed in the leaf dur- ing its lifetime is estimated to be between 15,000 and 60,000 (Flavell 1980). Of these, only about 6,000 genes appear to be leaf-specific (Goldberg 1988). However, mRNA expression in the leaf has not been thoroughly stud- ied. For instance, 709 EST sequences have been reported in the Arabidopsis leaf (Cooke et al. 1996), and 53 ESTs were obtained from leaf strips grown in a medium contain- ing 2,4-dichlorophenoxy-acetic acid. These genes, how- ever, may have been expressed under a specific stress con- dition caused by the media. In addition, there is no pub- lished report that focuses on leaf ESTs generated from rice (Yamamoto and Sasaki 1997). In previous cDNA sequencing studies in Brassica, the majority of ESTs were derived from cDNAs isolated from the roots (B. napus 197 ESTs, Park et al. 1993), flower bud (B. campestris, 1,216 ESTs, Lim et al. 1996) and guard cell (B. campestris, 515 ESTs, Kwak et al. 1997). Thus, an over- view of gene diversity and expression patterns in the in- tact leaf of B. napus has not been reported. In this study, we chose to investigate the leaf of B. na- pus because the leaf provides an interesting subject for the study of plant organ development and cellular differentia- tion. Therefore, the generation of ESTs from the leaf of Plant Cell Reports (1998) 17: 930–936 © Springer-Verlag 1998 Received: 21 October 1997 / Revision received: 25 March 1998 / Accepted: 17 April 1998 C. M. Lee · Y. J. Lee · M. H. Lee · H. G. Nam T. J. Cho · T. R. Hahn · M. J. Cho · U. Sohn Large-scale analysis of expressed genes from the leaf of oilseed rape (Brassica napus L.) The nucleotide sequence data reported in this article have been loaded into the GenBank, the EMBL Data Library, the DNA Data Bank of Japan, and the National Center for Biotechnology Infor- mation under the following accession numbers; H06410-H06429, H07149-H07194, H07205-H07853, H10686, T18340-T18370, T18372-T18378. Communicated by K. Syono C. M. Lee · Y. J. Lee · M. H. Lee · U. Sohn () Department of Genetic Engineering, Kyungpook National University, Taegu 702-701, Korea Fax: +82-53-955-5327 e-mail: usohn@bh.kyungpook.ac.kr H. G. Nam Department of Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea T. J. Cho Department of Biochemistry, Chung-buk National University, Chengju 360-763, Korea T. R. Hahn Department of Genetic Engineering, Kyung Hee University, Seoul 130-701, Korea M. J. Cho Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Chinju 660-701, Korea