Molecular cloning and expression analysis of CONSTANS homologs from Gypsophila paniculata

To better understand the molecular mechanism of the photoperiodic flowering pathway in commercially important flowers, we performed cDNA cloning and analyzed the expression of CONSTANS (CO) homologs in Gypsophila paniculata, a popular cut flower in which flowering is clearly induced by long-day treatment. RNA was extracted from G. paniculata leaves sampled at 09:00 and 19:00 h. Reverse transcription-PCR was carried out using primers based on the amino acid sequences of the conserved region of CO homologs from several species, followed by 3'-RACE using the PCR fragment. The sequencing results suggest that at least four CO homologs exist and are expressed in G. paniculata: GpCOL1, GpCOL2, GpCOL3, and GpCOL4. The four CO homologs contained a CCT (CO, CO-like, TOC1) domain near the carboxyl terminus. Phylogenetic analysis of CCT domain amino acids showed that the four GpCOLs are involved in Group I of the CO-like proteins. The expression of GpCOL2 and GpCOL3 showed daily oscillations, suggesting a relationship between these GpCOLs and photoperiod response in G. paniculata.