Abstract: Derived from tomato and influenced by circadian clock, a TDF(transcription-drived fragments, TDF)was used as a seed sequence for searching homologous ESTs through electronical elongation in NCBI database. A full-length CONSTANS-Like gene designed as SlCO1(GenBank accession number, EU636698), is cloned using RT-PCR. The deduced SlCO1 protein consisting of 386 amino acid residues contains two B-box zinc finger motifs near the amino terminus and a conserved CCT domain near the carboxy terminus. Moreover, a 535 bp intron is located between the B-box and CCT domain. Although SlCO1 proteins shares 34 %~46 % identity with other CO proteins, the deduced amino acid sequence is highly conserved in the B-box and CCT domain. SlCO1 expresses specifically and strongly in leaf, but weakly in roots and stems. Cloning of SlCO1 will provide a scientific basis for understanding the role of CONSTANS-like genes in tomato flowering process.

Key words: Tomato, Solanum lycopersicum, flowering time, CONSTANS-like gene