Asymmetric gibberellin signaling regulates vacuolar trafficking of PIN auxin transporters during root gravitropism

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Authors

LOEFKE Christian ZWIEWKA Marta HEILMANN Ingo VAN MONTAGU Marc C E TEICHMANN Thomas FRIML Jiří

Year of publication 2013
Type Article in Periodical
Magazine / Source Proc. Natl. Acad. Sci. U. S. A.
MU Faculty or unit

Central European Institute of Technology

Citation
Web http://www.pnas.org/content/110/9/3627
Doi http://dx.doi.org/10.1073/pnas.1300107110
Field Genetics and molecular biology
Keywords hormone cross-talk; protein stability; protein trafficking
Attached files
Description Gravitropic bending of plant organs is mediated by an asymmetric signaling of the plant hormone auxin between the upper and lower side of the respective organ. Here, we show that also another plant hormone, gibberellie acid (GA), shows asymmetric action during gravitropic responses. lmmunodetection using an antibody against GA and monitoring GA signaling output by downstream degradation of DELLA proteins revealed an asymmetric GA distribution and response with the maximum at the lower side of gravistimulated roots. Genetic or pharmacological manipulation of GA levels or response affects gravity-mediated auxin redistribution and root bending response. The higher GA levels at the lower side of the root correlate with increased amounts of PIN-FORMED2 (PIN2) auxin transporter at the plasma membrane. The observed increase in PIN2 stability is caused by a specific GA effect on trafficking of PIN proteins to lytic vacuoles that presumably occurs downstream of brefeldin A-sensitive endosomes. Our results suggest that asymmetric auxin distribution instructive for gravity-induced differential growth is consolidated by the asymmetric action of GA that stabilizes the PIN-dependent auxin stream along the lower side of gravistimulated roots.
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