The expression of genes specific to floral organ is important for the floral organ formation and development in Medicago truncatula. Screening of the genes specifically expressed in M. truncatula flowers and comparing the expression patterns of their orthologous homologous genes among different model plants can provide novel insights into the functions of these genes in controlling the floral organ development in M. truncatula. According to the expression profile data of PISTILLATA (PI), we screened 97 genes specifically expressed in M. truncatula floral organs (ratio≥10 and Z≥7.9). Their homolog genes were also identified in Arabidopsis thaliana, soybean (Glycine max L.), Lotus japonicus, and rice (Oryza sativa L.). The results of comparing the gene expression levels, the gene expression patterns, and the gene functions among these species indicated that the expression variation of the orthologous homolog genes was small in the kindred species and was great in distant species. Furthermore, we compared the cis-acting regulatory elements of the genes, which had large expression variation among different plants. These results suggest that the great discrepancy of the orthologous homolog gene expression caused by the different character of cis-element in the promoter region.
[1] Sawa S, Watanabe K, Goto K, Liu YG, Shibata D, Kanaya E, Morita EH, Okada K. FILAMENTOUS FLOWER, a meristem and organ identity gene of Arabidopsis, encodes a protein with a zinc finger and HMG-related domains. Genes Dev, 1999 13(9): 1079-1088.
[2] Coen ES, Meyerowitz EM. The war of the whorls: genetic interactions controlling flower development. Nature, 1991, 353(6339): 31-37.
[3] Theissen G, Saedler H. Plant biology: Floral quartets. Nature, 2001, 409(6819): 469-471.
[4] Honma T, Goto K. Complexes of MADS-box proteins are sufficient to convert leaves into floral organs. Nature, 2001, 409(6819): 525-529.
[5] Benlloch R, Berbel A, Serrano-Mislata A, Madueño F. Floral initiation and inflorescence architecture: A comparative view. Ann Bot-London, 2007, 100(3): 659-676.
[6] Tang MF, Li GS, Chen MS. The phylogeny and expression pattern of APETALA2-like genes in rice. J Genet Genomics, 2007, 34(10): 930-938.
[7] Foucher F, Morin J, Courtiade J, Cadioux S, Ellis N, Banfield MJ, Rameau C. DETERMINATE and LATE FLOWERING are two TERMINAL FLOWER1/CENTRORADIALIS homologs that control two distinct phases of flowering initiation and develop-ment in pea. Plant Cell, 2003, 15(11): 2742-2754.
[8] 潘增祥, 许丹, 张金璧, 林飞, 吴宝江, 刘红林. 基于直向同源序列的比较基因组学研究. 遗传, 2009, 31(5): 457-463.
[9] Wendel JF. Genome evolution in polyploids. Plant Mol Biol, 2000, 42(1): 225-249.
[10] Sonnhammer ELL, Koonin EV. Orthology, paralogy and proposed classification for paralog subtypes. Trends Genet, 2002, 18(12): 619-620.
[11] 刘志鹏, 王能飞, 赵爱云, 沈继红, 刘小丽, 刘公社. 低拷贝核基因在异源多倍体植物中的进化与表达. 遗传, 2007, 29(2): 163-171.
[12] Coen ES, Romero JM, Doyle S, Elliott R, Murphy G, Carpenter R. Floricaula: a homeotic gene required for flower development in Antirrhinum majus. Cell, 1990, 63(6): 1311-1322.
[13] Weigel D, Alvarez J, Smyth DR, Yanofsky MF, Mey-erowitz EM. LEAFY controls floral meristem identity in Arabidopsis. Cell, 1992, 69(5): 843-859.
[14] Hofer J, Turner L, Hellens R, Ambrose M, Matthews P, Michael A, Ellis N. UNIFOLIATA regulates leaf and flower morphogenesis in pea. Curr Biol, 1997, 7(8): 581-587.
[15] Zhang SL, Sandal N, Polowick PL, Stiller J, Stougaard J, Fobert PR. Proliferating floral organs (PFO), a Lotus japonicus gene required for specifying floral meristem determinacy and organ identity, encodes an F-box protein. Plant J, 2003, 33(4): 607-619.
[16] Taylor A, Hofer J, Murfet I. Stamina pistilloida, the pea ortholog of FIM and UFO, is required for normal development of flowers, inflorescences, and leaves. Plant Cell, 2001, 13(1): 31-46.
[17] Nair R, Howie J, Delalande M. Medicago truncatula cultivars. Medicago truncatula Handbook, 2006, 11: 1-14.
[18] Bowman JL, Smyth DR, Meyerwitz EM. Genes directing flower development in Arabidopsis. Plant Cell, 1989, 1(1): 37-52.
[19] Hecht V, Foucher F, Ferrándiz C, Macknight R, Navarro C, Morin J, Vardy ME, Ellis N, Beltrán JP, Rameau C, Weller JL. Conservation of Arabidopsis flowering genes in model legumes. Plant Physiol, 2005, 137(4): 1420-1434.
[20] Barker DG, Bianchl S, Blondon F, Dattée Y, Duc G, Essad S, Flament P, Gallusci P, Génier G, Guy P. Medicago truncatula, a model plant for studying the molecular genetics of the rhizobium-legume symbiosis. Plant Mol Biol Rep, 1990, 8(1): 40-49.
[21] Endre G, Kereszt A, Kevei Z, Mihacea S, Kaló P, Kiss GB. A receptor kinase gene regulating symbiotic nodule de-velopment. Nature, 2002, 417(6892): 962-966.
[22] Li MN, Xu WY, Yang WQ, Kong ZS, Xue YB. Ge-nome-wide gene expression profiling reveals conserved and novel molecular functions of the stigm
