ABSTRACT
A novel gene, designated PnFL-1, was isolated from flower-induced cotyledons in a short-day plant, Pharbitis nil, using messenger RNA differential display. PnFL-1 has no similarity to genes with known functions in databases, but the deduced amino acid sequence of the gene has 58% homology with a hypothetical protein of Arabidopsis including a phosphatidic acid phosphatase 2 domain. PnFL-1 is a single-copy gene that is expressed during the inductive dark period. Expression of PnFL-1 increased gradually from the 6th to 16th h of a 16-h dark period, and expression was extinguished by a brief exposure to light at the 8th hour of the dark period (night break treatment). PnFL-1 mRNA was found in cotyledons and leaves but not in stems and roots. These results indicate that the transcription of PnFL-1 in Pharbitis may be photoperiodically regulated and associated with photoperiodic events.
Subject(s)
Cotyledon/physiology , Flowers/metabolism , Genes, Plant , Plant Proteins/metabolism , Plants/metabolism , Amino Acid Sequence , Base Sequence , DNA, Plant , Gene Expression Regulation, Plant , Molecular Sequence Data , Photoperiod , Plant Proteins/genetics , Plants/anatomy & histology , Plants/genetics , RNA, Messenger/metabolism , Sequence Alignment , Tissue DistributionABSTRACT
The Arabidopsis CONSTANS (CO) gene is a key regulator of the long day (LD)-dependent flowering pathway and two CO homologous genes COL1 and COL2 are involved in the regulation of the circadian rhythm. In order to understand the role of CO and COL in short-day plants, a CO homologue, PnCOL1, was isolated and characterized from Japanese morning glory (Pharbitis nil). The deduced PnCOL1 protein of 386 amino acid residues contained two putative zinc finger motifs at the N-terminal region and a conserved CCT domain at the C-terminal region. The deduced amino acid sequence of PnCOL1 was 34% identical to that of PnCO, but 32%, 34%, and 34% identical to those of CO, COL1, and COL2, respectively. Expression of PnCOL1 was barely detected in the cotyledons of plants grown under continuous light (CL), but highly expressed in the cotyledons of plants grown under SD. Expression of PnCOL1 showed a pattern of circadian rhythm as well as daily oscillation. The overexpression of PnCOL1 by a 35S promoter did not overcome the late-flowering phenotype of Arabidopsis co mutants. The results provided in this study suggest that PnCOL1 may have a role in the circadian rhythm in Pharbitis nil.
