Interspecific divergence of circadian properties in duckweed plants

<jats:title>Abstract</jats:title><jats:p>The circadian clock system is widely conserved in plants; however, divergence in circadian rhythm properties is poorly understood. We conducted a comparative analysis of the circadian properties of closely related duckweed species. Using a particle bombardment method, a circadian bioluminescent reporter was introduced into duckweed plants. We measured bioluminescence circadian rhythms of eight species of the genus <jats:italic>Lemna</jats:italic> and seven species of the genus <jats:italic>Wolffiella</jats:italic> at various temperatures (20, 25, and 30°C) and light conditions (constant light or constant dark). <jats:italic>Wolffiella</jats:italic> species inhabit relatively warm areas and lack some tissues/organs found in <jats:italic>Lemna</jats:italic> species. <jats:italic>Lemna</jats:italic> species tended to show robust bioluminescence circadian rhythms under all conditions, while <jats:italic>Wolffiella</jats:italic> species showed lower rhythm stability, especially at higher temperatures. For <jats:italic>Lemna</jats:italic>, two species (<jats:italic>L. valdiviana</jats:italic> and <jats:italic>L. minuta</jats:italic>) forming a clade showed relatively lower circadian stability. For <jats:italic>Wolffiella</jats:italic>, two species (<jats:italic>W. hyalina</jats:italic> and <jats:italic>W. repanda</jats:italic>) forming a clade showed extremely long period lengths. These analyses reveal that the circadian properties of species primarily reflect their phylogenetic positions. The relationships between geographical and morphological factors and circadian properties are also suggested.</jats:p>