摘要
The process of flowering is controlled by a hierarchy of floral genes that act as flowering time genes, inflorescence/floral meristem Identity genes, and/or floral organ-identity genes. The most important and well-characterized floral genes are those that belong to the MADS-box family of transcription factors. Compelling evidence suggests that floral MADS-box genes have experienced a few large-scale duplication events. In particular, the precore eudicot duplication events have been considered to correlate with the emergence and diversification of core eudicots. Duplication of floral MADS-box genes has also been documented in monocots, particularly In grasses, although a systematic study is lacking. In the present study, by conducting extensive phylogenetlc analyses, we identified pre-Poaceae gene duplication events in each of the AP1, P1, AG, AGL11, AGL2/3/4, and AGL9gene lineages. Comparative genomic studies further indicated that some of these duplications actually resulted from the genome doubling event that occurred 66-70 million years ago （MYA）. In addition, we found that after gene duplication, exonization （of intron sequences） and pseudoexonization （of exon sequences） have contributed to the divergence of duplicate genes in sequence structure and, possibly, gene function.
The process of flowering is controlled by a hierarchy of floral genes that act as flowering time genes, inflorescence/floral meristem Identity genes, and/or floral organ-identity genes. The most important and well-characterized floral genes are those that belong to the MADS-box family of transcription factors. Compelling evidence suggests that floral MADS-box genes have experienced a few large-scale duplication events. In particular, the precore eudicot duplication events have been considered to correlate with the emergence and diversification of core eudicots. Duplication of floral MADS-box genes has also been documented in monocots, particularly In grasses, although a systematic study is lacking. In the present study, by conducting extensive phylogenetlc analyses, we identified pre-Poaceae gene duplication events in each of the AP1, P1, AG, AGL11, AGL2/3/4, and AGL9gene lineages. Comparative genomic studies further indicated that some of these duplications actually resulted from the genome doubling event that occurred 66-70 million years ago （MYA）. In addition, we found that after gene duplication, exonization （of intron sequences） and pseudoexonization （of exon sequences） have contributed to the divergence of duplicate genes in sequence structure and, possibly, gene function.
基金
Supported by the National Natural Science Foundation of China （30530090, 30470116 and 30121003） and Institute of Botany, the Chinese Academy of Sciences. Publication of this paper is supported by the National Natural Science Foundation of China （30624808）.Acknowledgements The authors thank Drs Hong Ma （Department of Biology and the Huck Institute of Life Sciences, Pennsylvania State University, USA） and Hongyan Shan （Institute of Botany, the Chinese Acad- emy of Sciences, Beijing, China）, and Yang Liu, Jian Zhang, and Jin Hu （Institute of Botany, the Chinese Academy of Sciences, Beijing, China） for their critical reading of the manuscript and their valuable comments. The authors also thank Dr Yang Zhong （School of Life Sciences, Fudan University） for helpful suggestions.
