title: Light and circadian regulation in the expression of LHY and Lhcb genes in Phaseolus vulgaris.
abstract: In order to understand some aspects of the circadian clock function in Phaseolus vulgaris, we analyzed the temporal transcript profile of Lhcb genes, typical clock reporters in plants, and that of PvLHY, an orthologue of Arabidopsis thaliana LHY which is a putative transcription factor of Lhcb genes. Under different light regimes, Lhcb and PvLHY exhibit a clear circadian pattern of expression. Moreover, the rhythm of Lhcb genes appears to be tightly coupled to that of PvLHY with the latter having a slightly earlier phase. This supports the idea that the oscillating capacity of PvLHY may be one of the causes of the rhythmic expression of Lhcb genes in bean. In addition to their circadian regulation, Lhcb and PvLHY are induced by light with similar and relatively slow induction kinetics. Moreover, this light induction is gated by the circadian oscillator: minimal responses occur at times around peaks of the pre-existing rhythm, while maximal ones occur at troughs of the pre-existing rhythm. This pattern of gating is opposite to that observed in Arabidopsis. The failure to block the light induction pathways at pre-existing troughs appears to have a detrimental effect to the subsequent circadian rhythmicity. Briefly, the overall regulation of PvLHY and Lhcb genes by light and the circadian clock reveals different strategies between Phaseolus and Arabidopsis in the adaptation to photoperiodic conditions.
authors.affiliation: Institute of Biology, NCSR 'Demokritos', 15310 Aghia Paraskevi, Attiki, Greece.
authors.forename: Athanasios-Dimitrios
authors.initials: AD
authors.lastname: Kaldis
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Kousidis
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Kesanopoulos
authors.forename: Anastasia
authors.initials: A
authors.lastname: Prombona
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002940:Circadian Rhythm / Q000502:physiology*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004268:DNA-Binding Proteins / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D008027:Light; D008969:Molecular Sequence Data; D027805:Phaseolus / Q000235:genetics* / Q000528:radiation effects; D017440:Photoperiod; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D014157:Transcription Factors