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Insights into ROS-dependent signalling underlying transcriptomic plant responses to the herbicide 2,4-D

ABSTRACT: The synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) functions as an agronomic weed control herbicide. High concentrations of 2,4-D induce plant growth defects, particularly leaf epinasty and stem curvature. Although the 2,4-D phenotype is associated with ROS production, little is known about ROS-dependent signalling. In this study, by using T-DNA Arabidopsis mutants to silence peroxisomal acyl CoA oxidase 1 (acx1-2), we identified ACX1 as one of the main sources of ROS production and as partly the cause of the epinasty phenotype following the application of 2,4-D. Transcriptomic analyses of WT plants after treatment with 2,4-D revealed a ROS-related peroxisomal footprint in early plant responses, while other organelles, such as mitochondria and chloroplasts, are involved in later responses. Interestingly, a group of ACX1-dependent transcripts in plant responses to 2,4-D, previously associated with epinasty, is related to auxin biosynthesis, metabolism and signalling. We found that protein AUXIN SIGNALING F-BOX 3 (AFB3), a component of SCF (ASK-cullin-F-box) E3 ubiquitin ligase complexes, which functions as an auxin receptor and mediates Aux/IAA proteasomal degradation, acts downstream of ACX1 and is involved in the epinasty phenotype induced by 2,4-D. We also found that protein degradation associated with ubiquitin E3-RING and E3-SCF-FBOX in ACX1-dependent signalling in plant responses to 2,4-D is significantly regulated over longer treatment periods.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE179303 | GEO | 2021/12/01

REPOSITORIES: GEO

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Project description: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.

Project description: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 temporal regulation of the movement of flowers we used a whole genome microarray as a discovery platform to identify genes differentially expressed in a RNAi knockdown line silenced in the expression of the circadian clock component ZEITLUPE (irZTL-314).

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Insights into ROS-dependent signalling underlying transcriptomic plant responses to the herbicide 2,4-D

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