Flowering initiation depends on the balanced expression of a complex network of genes that is regulated by both endogenous and environmental factors. The timing of the initiation of flowering is crucial for the reproductive success of plants; therefore, they have developed conserved molecular mechanisms to integrate both environmental and endogenous cues to regulate flowering time precisely. Extensive advances in plant biology are possible now that the complete genome sequences of flowering plants is available and plant genomes can be comprehensively compared. Thus, association studies are emerging as powerful tools for the functional identification of genes involved on the regulation of flowering pathways. In this paper we report the results of our search in the Eucalyptus Genome Sequencing Project Consortium (FORESTS) database for expressed sequence tags (ESTs) showing sequence homology with known elements of flowering-time pathways. We have searched the 33,080 sequence clusters in the FORESTS database and identified Eucalyptus sequences that codify putative conserved elements of the autonomous, vernalization-, photoperiod response- and gibberellic acid-controlled flowering-time pathways. Additionally, we have characterized in silico ten putative members of the Eucalyptus homologs to the Arabidopsis CONSTANS family of transcription factors.172255266Adams, J., Kelso, R., Cooley, L., The kelch repeat superfamily of proteins: Propellers of cell function (2000) Trends Cell Biol., 10, pp. 17-24Alabadi, D., Oyama, T., Yanovsky, M.J., Harmon, F.G., Mas, P., Kay, S.A., Reciprocal regulation between TOC1 and LHY/CCA1 within the Arabidopsis circadian clock (2001) Science, 293, pp. 880-883Altschul, S.F., Madden, T.L., Schäffer, A.A., Zhang, J., Zhang, Z., Miller, W., Lipman, D.J., Gapped BLAST and PSI-BLAST: A new generation of protein database seach programs (1997) Nucl. Acids Res., 25, pp. 3389-3402Araki, T., Transition from vegetative to reproductive phase (2001) Curr. Opin. Plant Biol., 4, pp. 63-68Bagnall, D.J., King, R.W., Whitelam, G.C., Boylan, M.T., Wagner, D., Quail, P.H., Flowering responses to altered expression of phytochrome in mutants and transgenic lines of Arabidopsis thaliana (L) Heynh. (1995) Plant Physiol., 108, pp. 1495-1503Battey, N.H., Aspects of seasonally (2000) J. Exp. Bot., 51, pp. 1769-1780Birve, A., Sengupta, A.K., Beuchle, D., Larsson, J., Kennison, J.A., Rasmuson-Lestander, A., Muller, J., Su(z)12 a novel Drosophila Polycomb group gene that is conserved in vertebrates and plants (2001) Development, 128, pp. 3371-3379Blazquez, M.A., Weigel, D., Integration of floral inductive signals in Arabidopsis (2000) Nature, 404, pp. 889-892Blazquez, M.A., Green, R., Nilsson, O., Sussman, M.R., Weigel, D., Gibberellins promote flowering of Arabidopsis by activating the LEAFY promoter (1998) Plant Cell, 10, pp. 791-800Borden, K.L.B., RING fingers and B-boxes: Zinc-binding protein-protein interaction domains (1998) Biochem. Cell Biol., 76, pp. 351-358Borner, R., Kampmann, G., Chandler, J., Gleissner, R., Wisman, E., Apel, K., Melzer, S., A MADS domain gene involved in the transition to flowering in Arabidopsis (2000) Plant J., 24, pp. 591-599Briggs, W.R., Huala, E., Blue-light photoreceptors in higher plants (1999) Annu. Rev. Cell Dev. Biol., 15, pp. 33-62Burn, J.E., Bagnall, D.J., Metzger, J.D., Dennis, E.S., Peacock, W.J., DNA methylation vernalization and the initiation of flowering (1993) Proc. Natl. Acad. Sci. USA, 90, pp. 287-291Clarke, J.H., Dean, C., Mapping FRI a locus controlling flowering time and vernalization response in Arabidopsis thaliana (1994) Mol. Gen. Genet., 242, pp. 81-89Corbesier, L., Gadisseur, I., Silvestre, G., Jacqmard, A., Bernier, G., Design in Arabidopsis thaliana of a synchronous system of floral induction by one long day (1996) Plant J., 9, pp. 947-952Dornelas, M.C., Rodriguez, A.P.M., A genomic approach to elucidating grass flower development (2001) Gen. Mol. Biol., 24, pp. 69-76Dornelas, M.C., Rodriguez, A.P.M., Identification of differentially expressed genes during reproductive development in sugarcane (Saccharum sp) by the analysis of expressed sequence tags (2004) Flowering Newsletter, 37, pp. 40-45Dornelas, M.C., Amaral, W.A.N., Rodriguez, A.P.M., EgLFY, the Eucalyptus grandis homolog of the Arabidopsis gene LFY is expressed in reproductive and vegetative tissues (2004) Braz. J. Plant Physiol., 16, pp. 105-114Fowler, S., Lee, K., Onouchi, H., Samach, A., Richardson, K., Coupland, G., Putterill, J., GIGANTEA: A circadian clock-controlled gene that regulates photoperiodic flowering in Arabidopsis and encodes a protein with several possible membrane-spanning domains (1999) EMBO J., 18, pp. 4679-4688Gendall, A.R., Levy, Y.Y., Wilson, A., Dean, C., The VERNALIZATION 2 gene mediates the epigenetic regulation of vernalization in Arabidopsis (2001) Cell, 107, pp. 525-535Griffiths, S., Dunford, R.D., Coupland, G., Laurie, D.A., The evolution of the CONSTANS-like gene families in barley, rice and Arabidopsis (2003) Plant Physiol., 131, pp. 1855-1867Guo, H.W., Duong, H., Ma, N., Lin, C.T., The Arabidopsis blue light receptor cryptochrome 2 is a nuclear protein regulated by a blue light-dependent post-transcriptional mechanism (1999) Plant J., 19, pp. 279-287Guo, H.W., Yang, W.Y., Mockler, T.C., Lin, C.T., Regulations of flowering time by Arabidopsis photoreceptors (1998) Science, 279, pp. 1360-1363Hall, T.A., BioEdit: A user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT (1999) Nucl. Acids Symp. Ser., 41, pp. 95-98Hicks, K.A., Albertson, T.M., Wagner, D.R., EARLY FLOWERING3 encodes a novel protein that regulates circadian clock function and flowering in Arabidopsis (2001) Plant Cell, 13, pp. 1281-1292Huq, E., Tepperman, J.M., Quail, P.H., GIGANTEA is a nuclear protein involved in phytochrome signaling in Arabidopsis (2000) Proc. Natl. Acad. Sci. USA, 97, pp. 9789-9794Izawa, T., Takahashi, Y., Yano, M., Comparative biology comes into bloom: Genomic and genetic comparison of flowering pathways in rice and Arabidopsis (2003) Curr. Opin. Plant Biol., 6, pp. 113-120Jarillo, J.A., Capel, J., Tang, R.-H., Yang, H.-Q., Alonso, J.M., Ecker, J.R., Cashmore, A.R., An Arabidopsis circadian clock component interacts with both CRY1 and phyB (2001) Nature, 410, pp. 487-490Johanson, U., West, J., Lister, C., Michaels, S., Amasino, R., Dean, C., Molecular analysis of FRIGIDA a major determinant of natural variation in Arabidopsis flowering time (2000) Science, 290, pp. 344-347Johnson, E., Bradley, M., Harberd, N.P., Whitelam, G.C., Photoresponses of light-grown phyA mutants of Arabidopsis: Phytochrome A is required for the perception of day length extensions (1994) Plant Physiol., 105, pp. 141-149Kardailsky, I., Shukla, V.K., Ahn, J.H., Dagenais, N., Christensen, S.K., Nguyen, J.T., Chory, J., Weigel, D., Activation tagging of the floral inducer FT (1999) Science, 286, pp. 1962-1965Kinoshita, T., Harada, J.J., Goldberg, R.B., Fischer, R.L., Polycomb repression of flowering during early plant development (2001) Proc. Natl. Acad. Sci. USA, 98, pp. 14156-14161Kobayashi, Y., Kaya, H., Goto, K., Iwabuchi, M., Araki, T., A pair of related genes with antagonistic roles in mediating flowering signals (1999) Science, 286, pp. 1960-1962Koornneef, M., Blankestijn-de-Vries, H., Hanhart, C., Soppe, W., Peeters, T., The phenotype of some late-flowering mutants is enhanced by a locus on chromosome 5 that is not effective in the Landsberg erecta wild-type (1994) Plant J., 6, pp. 911-919Koornneef, M., Hanhart, C.J., Van Der Veen, J.H., A genetic and physiological analysis of late flowering mutants in Arabidopsis thaliana (1991) Mol. Gen. Genet., 229, pp. 57-66Kreps, J.A., Simon, A.E., Environmental and genetic effects on circadian clock-regulated gene expression in Arabidopsis (1997) Plant Cell, 9, pp. 297-304Lagercrantz, U., Axelsson, T., Rapid evolution of the family of CONSTANS like genes in plants (2000) Mol. Biol. Evol., 17, pp. 1499-1507Lee, H., Suh, S.-S., Park, E., Cho, E., Ahn, J.H., Kim, S.-G., Lee, J.S., Lee, I., The AGAMOUS-LIKE 20 MADS domain protein integrates floral inductive pathways in Arabidopsis (2000) Genes Dev., 14, pp. 2366-2376Lee, I.A.B., Amasino, R., Analysis of naturally occurring late flowering in Arabidopsis thaliana (1993) Mol. Gen. Genet., 237, pp. 171-176Lee, Y., Lloyd, A.M., Roux, S.J., Antisense expression of the CK2 alpha-subunit gene in Arabidopsis Effects on light-regulated gene expression and plant growth (1999) Plant Physiol., 119, pp. 989-1000Levy, Y.Y., Dean, C., Control of flowering time (1998) Curr Opin Plant Biol, 1, pp. 49-54Levy, Y.Y., Mesnage, S., Mylne, J.S., Gendall, A.R., Dean, C., Multiple roles of Arabidopsis VRN1 in vernalization and flowering time control (2002) Science, 297, pp. 243-246Liu, X.L., Covington, M.F., Fankhauser, C., Chory, J., Wanger, D.R., ELF3 encodes a circadian clock-regulated nuclear protein that functions in an Arabidopsis PHYB signal transduction pathway (2001) Plant Cell, 13, pp. 1293-1304Marchler-Bauer, A., Anderson, J.B., Cherukuri, P.F., DeWeese-Scott, C., Geer, L.Y., Gwadz, M., He, S., Bryant, S.H., CDD: A Conserved Domain Database for protein classification (2005) Nucl. Acids Res., 33, pp. 192-196McClung, C.R., Circadian rhythms in plants (2001) Annu. Rev. Plant Physiol. Plant Mol. Biol., 52, pp. 139-162Michaels, S.D., Amasino, R.M., Memories of winter: Vernalization and the competence to flower (2000) Plant Cell Environ., 23, pp. 1145-1153Michaels, S.D., Amasino, R.M., Loss of FLOWERING LOCUS C activity eliminates the late-flowering phenotype of FRIGIDA and autonomous pathway mutations but not responsiveness to vernalization (2001) Plant Cell, 13, pp. 935-941Mizoguchi, T., Wheatley, K., Hanzawa, Y., Wright, L., Mizoguchi, M., Song, H.-R., Carré, I.A., Coupland, G., LHY and CCA1 are partially redundant genes required to maintain circadian rhythms in Arabidopsis (2002) Dev. Cell, 2, pp. 629-641Moncur, M.W., Hasan, O., Floral induction in Eucalyptus nitens (1994) Tree Physiol., 14, pp. 1303-1312Mouradov, A., Cremer, F., Coupland, G., Control of flowering time: Interacting pathways as a basis for diversity (2002) Plant Cell, (SUPPL.), pp. S11-S130Nelson, D.C., Lasswell, J., Rogg, L.E., Cohen, M.A., Bartel, B., FKF1 a clock-controlled gene that regulates the transition to flowering in Arabidopsis (2000) Cell, 101, pp. 331-340Ohad, N., Yadegari, R., Margossian, L., Hannon, M., Michaeli, D., Harada, J.J., Goldberg, R.B., Fischer, R.L., Mutations in FIE a WD polycomb group gene allow endosperm development without fertilization (1999) Plant Cell, 11, pp. 407-415Onouchi, H., Igeno, M.I., Perilleux, C., Graves, K., Coupland, G., Mutagenesis of plants overexpressing CONSTANS demonstrates novel interactions among Arabidopsis flowering-time genes (2000) Plant Cell, 12, pp. 885-900Park, D.H., Somers, D.E., Kim, Y.S., Choy, Y.H., Lim, H.K., Soh, M.S., Kim, H.J., Nam, H.G., Control of circadian rhythms and photoperiodic flowering by the Arabidopsis GIGANTEA gene (1999) Science, 285, pp. 1579-1582Peña, L., Martin-Trillo, M., Juarez, J., Pina, J.A., Navarro, L., Martinez-Zapater, J.M., Constitutive expression of Arabidopsis LEAFY or APETALA1 genes in citrus reduces their generation time (2001) Nature Biotechnol., 19, pp. 263-267Pineiro, M., Coupland, G., The control of flowering time and floral identity in Arabidopsis (1998) Plant Physiol., 117, pp. 1-8Putterill, J., Robson, F., Lee, K., Simon, R., Coupland, G., The CONSTANS gene of Arabidopsis promotes flowering and encodes a protein showing similarities to zinc finger transcription factors (1995) Cell, 80, pp. 847-857Reeves, P.H., Coupland, G., Response of plant development to environment: Control of flowering by daylength and temperature (2000) Curr. Opin. Plant Biol., 3, pp. 37-42Robson, F., Costa, M.M.R., Hepworth, S., Vizir, I., Pineiro, M., Reeves, P.H., Putterill, J., Coupland, G., Functional importance of conserved domains in the flowering-time gene CONSTANS demonstrated by analysis of mutant alleles and transgenic plants (2001) Plant J., 28, pp. 619-631Roenneberg, T., Merrow, M., Circadian clocks: Omnes viae Romam ducunt (2000) Curr Biol, 10, pp. R742-R745Saitou, N., Nei, M., The neighbour joining method: A new method for reconstructing phylogenetic trees (1987) Molec. Biol. Evol., 4, pp. 406-425Samach, A., Coupland, G., Time measurement and the control of flowering in plants (2000) Bioessays, 22, pp. 38-47Samach, A., Onouchi, H., Gold, S.E., Ditta, G.S., Schwarz-Sommer, Z., Yanofsky, M.F., Coupland, G., Distinct roles of CONSTANS target genes in reproductive development of Arabidopsis (2000) Science, 288, pp. 1613-1616Schaffer, R., Ramsay, N., Samach, A., Corden, S., Putterill, J., Carre, I.A., Coupland, G., The late elongated hypocotyl mutation of Arabidopsis disrupts circadian rhythms and the photoperiodic control of flowering (1998) Cell, 93, pp. 1219-1229Sheldon, C.C., Burn, J.E., Perez, P.P., Metzger, J., Edwards, J.A., Peacock, W.J., Dennis, E.S., The FLF MADS box gene: A repressor of flowering in Arabidopsis regulated by vernalization and methylation (1999) Plant Cell, 11, pp. 445-458Sheldon, C.C., Rouse, D.T., Finnegan, E.J., Peacock, W.J., Dennis, E.S., The molecular basis of vernalization: The central role of FLOWERING LOCUS C (FLC) (2000) Proc. Natl. Acad. Sci. USA, 97, pp. 3753-3758Simpson, G.G., Dean, C., Arabidopsis the Rosetta stone of flowering time? (2002) Science, 296, pp. 285-289Somers, D.E., Schultz, T.F., Milnamow, M., Kay, S.A., ZEITLUPE encodes a novel clock-associated PAS protein from Arabidopsis (2000) Cell, 101, pp. 319-329Somers, D.E., Webb, A.A.R., Pearson, M., Kay, S.A., The short-period mutant toc1-1 alters circadian clock regulation of multiple outputs throughout development in Arabidopsis thaliana (1998) Development, 125, pp. 485-494Southerton, S.G., Strauss, S.H., Olive, M.R., Harcourt, R.L., Decroocq, V., Zhu, X., Llewellyn, D.J., Dennis, E.S., Eucalyptus has a functional equivalent of the Arabidopsis floral meristem identity gene LEAFY (1998) Plant Mol. Biol., 37, pp. 897-910Strayer, C., Oyama, T., Schultz, T.F., Raman, R., Somers, D.E., Mas, P., Panda, S., Kay, S.A., Cloning of the Arabidopsis clock gene TOC1 an autoregulatory response regulator homolog (2000) Science, 289, pp. 768-771Suarez-Lopez, P., Wheatley, K., Robson, F., Onouchi, H., Valverde, F., Coupland, G., CONSTANS mediates between the circadian clock and the control of flowering in Arabidopsis (2001) Nature, 410, pp. 1116-1120Sung, Z.R., Belachew, A., Shunong, B., Bertrand-Garcia, R., EMF an Arabidopsis gene required for vegetative shoot development (1992) Science, 258, pp. 1645-1647Thompson, J.D., Higgins, D.G., Gibson, T.J., CLUSTAL W: Improving the sensitivity of progressive multiple sequence alignment through sequence weighting, positions-specific gap penalties and weight matrix choice (1994) Nucl. Acids Res., 22, pp. 4673-4680Wagner, D., Sablowski, R.W.M., Meyerowitz, E.M., Transcriptional activation of APETALA1 by LEAFY (1999) Science, 285, pp. 582-584Wang, Z.-Y., Tobin, E.M., Constitutive expression of the CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) gene disrupts circadian rhythms and suppresses its own expression (1998) Cell, 93, pp. 1207-1217Weigel, D., Nilsson, O., A developmental switch sufficient for flower initiation in diverse plants (1995) Nature, 377, pp. 495-500Wilson, R.N., Heckman, J.W., Somerville, C.R., Gibberelin is required for flowering in Arabidopsis thaliana under short days (1992) Plant Physiol., 100, pp. 403-408Yang, C.-H., Chen, L.-J., Sung, Z.R., Genetic regulation of shoot development in Arabidopsis: Role of the EMF genes (1995) Dev. Biol., 169, pp. 421-435Yanovsky, M.J., Mazzella, M.A., Casal, J.J., A quadruple photoreceptor mutant still keeps track of time (2000) Curr. Biol., 10, pp. 1013-1015