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Plant Cell Reports

, Volume 34, Issue 3, pp 483–494 | Cite as

GA3 enhances root responsiveness to exogenous IAA by modulating auxin transport and signalling in Arabidopsis

  • Guijun Li
  • Changhua Zhu
  • Lijun Gan
  • Denny Ng
  • Kai Xia
Original Paper

Abstract

Key message

We used auxin-signalling mutants, auxin transport mutants, and auxin-related marker lines to show that exogenously applied GA enhances auxin-induced root inhibition by affecting auxin signalling and transport.

Abstract

Variation in root elongation is valuable when studying the interactions of phytohormones. Auxins influence the biosynthesis and signalling of gibberellins (GAs), but the influence of GAs on auxins in root elongation is poorly understood. This study was conducted to investigate the effect of GA3 on Arabidopsis root elongation in the presence of auxin. Root elongation was inhibited in roots treated with both IAA and GA3, compared to IAA alone, and the effect was dose dependent. Further experiments showed that GA3 could modulate auxin signalling based on root elongation in auxin-signalling mutants and the expression of auxin-responsive reporters. The GA3-enhanced inhibition of root elongation observed in the wild type was not found in the auxin-signalling mutants tir1-1 and axr1-3. GA3 increased DR5::GUS expression in the root meristem and elongation zones, and IAA2::GUS in the columella. The DR5rev::GFP signal was enhanced in columella cells of the root caps and in the elongation zone in GA3-treated seedling roots. A reduction was observed in the stele of PAC-treated roots. We also examined the effect of GA3 on auxin transport. The enhanced responsiveness caused by GA3 was not observed in the auxin influx mutant aux1-7 or the efflux mutant eir1-1. Additional molecular data demonstrated that GA3 could promote auxin transport via AUX1 and PIN proteins. However, GA3-induced PIN gene expression did not fully explain GA-enhanced PIN protein accumulation. These results suggest that GA3 is involved in auxin-mediated primary root elongation by modulating auxin signalling and transport, and thus enhances root responsiveness to exogenous IAA.

Keywords

Auxin Root elongation Gibberellins Auxin transport Auxin signalling Crosstalk 

Notes

Acknowledgments

We thank Yue Shen for her assistance with confocal laser microscopy. This research was supported by National Natural Science Foundation of China (30871460) to Kai Xia.

Conflict of interest

The authors declare that they have no conflict of interest.

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© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Guijun Li
    • 1
  • Changhua Zhu
    • 1
  • Lijun Gan
    • 1
  • Denny Ng
    • 2
  • Kai Xia
    • 1
  1. 1.College of Life SciencesNanjing Agricultural UniversityNanjingChina
  2. 2.CH Biotech R&D Co. Ltd.XianxiTaiwan ROC

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