The genome of the mesopolyploid crop species Brassica rapa Wang, Xiaowu Wang Xiaowu Wang, Hanzhong Wang Hanzhong Wang, Jun Wang Jun Sun, Rifei Sun Rifei Wu, Jian Wu Jian Liu, Shengyi Liu Shengyi Bai, Yinqi Bai Yinqi Mun, Jeong-Hwan Mun Jeong-Hwan Bancroft, Ian Bancroft Ian Cheng, Feng Cheng Feng Huang, Sanwen Huang Sanwen Li, Xixiang Li Xixiang Hua, Wei Hua Wei Wang, Junyi Wang Junyi Wang, Xiyin Wang Xiyin Freeling, Michael Freeling Michael Pires, J Chris Pires J Chris Paterson, Andrew H Paterson Andrew H Chalhoub, Boulos Chalhoub Boulos Wang, Bo Wang Bo Hayward, Alice Hayward Alice Sharpe, Andrew G Sharpe Andrew G Park, Beom-Seok Park Beom-Seok Weisshaar, Bernd Weisshaar Bernd Liu, Binghang Liu Binghang Li, Bo Li Bo Liu, Bo Liu Bo Tong, Chaobo Tong Chaobo Song, Chi Song Chi Duran, Christopher Duran Christopher Peng, Chunfang Peng Chunfang Geng, Chunyu Geng Chunyu Koh, Chushin Koh Chushin Lin, Chuyu Lin Chuyu Edwards, David Edwards David Mu, Desheng Mu Desheng Shen, Di Shen Di Soumpourou, Eleni Soumpourou Eleni Li, Fei Li Fei Fraser, Fiona Fraser Fiona Conant, Gavin Conant Gavin Lassalle, Gilles Lassalle Gilles King, Graham J King Graham J Bonnema, Guusje Bonnema Guusje Tang, Haibao Tang Haibao Wang, Haiping Wang Haiping Belcram, Harry Belcram Harry Zhou, Heling Zhou Heling Hirakawa, Hideki Hirakawa Hideki Abe, Hiroshi Abe Hiroshi Guo, Hui Guo Hui Wang, Hui Wang Hui Jin, Huizhe Jin Huizhe Parkin, Isobel A P Parkin Isobel A P Batley, Jacqueline Batley Jacqueline Kim, Jeong-Sun Kim Jeong-Sun Just, Jérémy Just Jérémy Li, Jianwen Li Jianwen Xu, Jiaohui Xu Jiaohui Deng, Jie Deng Jie Kim, Jin A Kim Jin A Li, Jingping Li Jingping Yu, Jingyin Yu Jingyin Meng, Jinling Meng Jinling Wang, Jinpeng Wang Jinpeng Min, Jiumeng Min Jiumeng Poulain, Julie Poulain Julie Wang, Jun Wang Jun Hatakeyama, Katsunori Hatakeyama Katsunori Wu, Kui Wu Kui Wang, Li Wang Li Fang, Lu Fang Lu Trick, Martin Trick Martin Links, Matthew G Links Matthew G Zhao, Meixia Zhao Meixia Jin, Mina Jin Mina Ramchiary, Nirala Ramchiary Nirala Drou, Nizar Drou Nizar Berkman, Paul J Berkman Paul J Cai, Qingle Cai Qingle Huang, Quanfei Huang Quanfei Li, Ruiqiang Li Ruiqiang Tabata, Satoshi Tabata Satoshi Cheng, Shifeng Cheng Shifeng Zhang, Shu Zhang Shu Zhang, Shujiang Zhang Shujiang Huang, Shunmou Huang Shunmou Sato, Shusei Sato Shusei Sun, Silong Sun Silong Kwon, Soo-Jin Kwon Soo-Jin Choi, Su-Ryun Choi Su-Ryun Lee, Tae-Ho Lee Tae-Ho Fan, Wei Fan Wei Zhao, Xiang Zhao Xiang Tan, Xu Tan Xu Xu, Xun Xu Xun Wang, Yan Wang Yan Qiu, Yang Qiu Yang Yin, Ye Yin Ye Li, Yingrui Li Yingrui Du, Yongchen Du Yongchen Liao, Yongcui Liao Yongcui Lim, Yongpyo Lim Yongpyo Narusaka, Yoshihiro Narusaka Yoshihiro Wang, Yupeng Wang Yupeng Wang, Zhenyi Wang Zhenyi Li, Zhenyu Li Zhenyu Wang, Zhiwen Wang Zhiwen Xiong, Zhiyong Xiong Zhiyong Zhang, Zhonghua Zhang Zhonghua We report the annotation and analysis of the draft genome sequence of Brassica rapa accession Chiifu-401-42, a Chinese cabbage. We modeled 41,174 protein coding genes in the B. rapa genome, which has undergone genome triplication. We used Arabidopsis thaliana as an outgroup for investigating the consequences of genome triplication, such as structural and functional evolution. The extent of gene loss (fractionation) among triplicated genome segments varies, with one of the three copies consistently retaining a disproportionately large fraction of the genes expected to have been present in its ancestor. Variation in the number of members of gene families present in the genome may contribute to the remarkable morphological plasticity of Brassica species. The B. rapa genome sequence provides an important resource for studying the evolution of polyploid genomes and underpins the genetic improvement of Brassica oil and vegetable crops. 43 10 1035-1039 1035-1039 Nature Publishing Group 2011 1