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Published on: March 30, 2018
WAG2 represses apical hook opening downstream from gibberellin and PHYTOCHROME INTERACTING FACTOR 5
Björn C Willige1, Eri Ogiso-Tanaka, Melina Zourelidou
1Department of Plant Systems Biology, Center for Life and Food Sciences, Technische Universtität München, Emil-Ramann-Strasse 4, 85354 Freising, Germany.
Plant germination involves an apical hook, regulated by auxin and gibberellin (GA). This study reveals GA signaling controls WAG2 kinase, crucial for apical hook opening by modulating auxin transport via PIN proteins.
Area of Science:
- Plant biology
- Molecular genetics
- Hormone signaling
Background:
- Dicotyledonous plants form an apical hook during germination to protect the shoot apical meristem.
- Apical hook development involves auxin, ethylene, and gibberellin (GA) signaling pathways.
- The interplay between these hormones is critical for regulating hook formation, maintenance, and opening.
Purpose of the Study:
- To elucidate the molecular mechanism of auxin-Gibberellin (GA) crosstalk in apical hook opening.
- To identify the role of the WAG2 protein kinase in GA-regulated processes.
- To understand how WAG2 influences auxin transport during hook development.
Main Methods:
- Analysis of wag2 mutants in dark-grown seedlings.
- Investigating WAG2 gene expression downstream of GA signaling.
- Assessing the impact of WAG2 on auxin transport and PIN protein regulation.
- Studying the interaction between WAG2, PIF5, and DELLA proteins.
Main Results:
- WAG2 is a transcriptional target of GA signaling and is activated by PIF5.
- wag2 mutants exhibit defects in apical hook opening, correlating with altered WAG2 expression.
- WAG2 is essential for maintaining auxin maxima and proper PIN protein function in the hook.
- WAG2 directly phosphorylates PIN auxin efflux facilitators.
Conclusions:
- GA signaling regulates apical hook opening through the differential accumulation of WAG2.
- WAG2 acts as a key mediator of GA effects on auxin transport via PIN proteins.
- This mechanism highlights a novel crosstalk between GA and auxin in plant development.
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