The circadian movement of flowers in the wild tobacco reveals a role for ZEITLUPE in the temporal gating of auxin responses

ABSTRACT: Wild tobacco flowers wave rhythmically to facilitate specific pollinator interactions. This movement behavior is controlled by a regulatory network that involves the circadian clock- and auxin-signaling pathways. The plant hormone auxin, similarly to its function in tropic movements, acts as growth regulator in the circadian regulation of floral movement. Dorsoventral asymmetry in auxin levels and auxin transcriptional responses mediate the growth responses in the floral peduncle that make flowers move. Multiple components of the auxin-signaling pathway and auxin responses are under the control of circadian clock. However, it is unclear where these two pathways intersect and how collectively contribute to regulate specific rhythmic outputs. Here we found that the blue light photoreceptor and circadian clock component ZEITLUPE (ZTL) controls auxin responses through the regulation of the auxin-signaling pathway in a time-of-day and blue light specific manner. Abrogation of ZTL expression abolishes flower movement and the temporal gating of auxin-induced growth responses in the floral peduncle. ZTL regulates transcription and directly interacts with indole-3-acetic acid inducible 19 (IAA19), a circadian controlled gene that regulates development of curvature in moving organs. Indicating that ZTL modulates auxin sensitivity in part through the regulation of AUX/IAA transcriptional repressors. At night, growth responses in the peduncle to the synthetic auxin 2,4-D revealed that ZTL additionally controls auxin responses regulating auxin homeostasis. These results indicate that ZTL conveys temporal and environmental information, at multiple levels, into the auxin signaling-pathway and in this way sculpts the temporal gating of auxin responses that allow flowers to move. To gain further insight into the molecular basis of the movement of flowers we used a whole genome microarray as a discovery platform to identify genes differentially expressed in adaxial and abaxial sides of the floral peduncle at different stages of the movement.

ORGANISM(S): Nicotiana attenuata

PROVIDER: GSE117235 | GEO | 2020/01/31

REPOSITORIES: GEO