The molecular mechanism underlying the periodic induction of lateral roots, a paradigmatic example of clock-driven organ formation in plant development, is a matter of ongoing, controversial debate. Here, we provide experimental evidence that this clock is frequency modulated by light and that auxin serves as a mediator for translating continuous light signals into discontinuous gene activation signals preceding the initiation of lateral roots in Arabidopsis seedlings. Based on this evidence, we propose a molecular model of an ultradian biological clock involving auxin-dependent degradation of an AUX/IAA-type transcription repressor as a flexible, frequency-controlling delay element. This model widens the bandwidth of biological clocks by adding a new type that allows the pace of organ formation to adapt to the changing environmental demands of the growing plant.
Keywords: Arabidopsis; Auxin; Environmental signal; Frequency modulation; Non-circadian oscillation; Organ patterning; Root development.
© 2018. Published by The Company of Biologists Ltd.