Overexpression of a <i>CO</i> homologue disrupts the rhythmic expression of clock gene <i>LgLHYH1</i> in <i>Lemna gibba</i>
In plants, the circadian clock is involved in the regulation of various physiological phenomena. The Arabidopsis <i>CONSTANS</i> gene (<i>AtCO</i>), a central component in photoperiodic flowering, as well as the <i>CONSTANS-LIKE 1</i> gene (<i>AtCOL1</i>), which has been suggested to be involved in the light input pathway, belong to the <i>CONSTANS-LIKE</i> gene family (<i>COL</i> family). To investigate the function of the <i>COL</i> family in the circadian system, we characterized <i>CO</i> homologues in two <i>Lemna</i> plant species (<i>LgCOH1</i> in <i>L. gibba</i> G3 and <i>LaCOH1</i> in <i>L. aequinoctialis</i> 6746). The expression of <i>LgCOH1</i> was upregulated by light, showing diurnal rhythmic expression with peak expression during daytime. We examined the effect of <i>LgCOH1</i> overexpression (<i>LgCOH1-ox</i>) on a circadian bioluminescent reporter. <i>LgCOH1-ox</i> damped the circadian bioluminescence rhythm, suggesting that it disturbed the circadian system. The overproduction of the N-terminal region including the zinc finger regions, or the C-terminal region including the CCT domain of <i>LgCOH1</i> damped the circadian bioluminescence rhythm, suggesting that both regions were involved in the phenotypic abnormalities found in the full-length <i>LgCOH1-ox</i> mutant. The overexpression of <i>AtCO</i> also damped the circadian bioluminescence rhythm in our co-transfection assay using <i>Lemna</i> plants, while its effect on the circadian rhythm was weaker than that of <i>LgCOH1-ox</i>. Based on these results, we suggest that some <i>COL</i> family genes may function in the regulation of the circadian system including the light input pathway.
- Plant Biotechnology
Plant Biotechnology, 2014
Japanese Society for Plant Cell and Molecular Biology