J Integr Plant Biol ›› 2020, Vol. 62 ›› Issue (5): 614-630.DOI: 10.1111/jipb.12813

• Molecular Physiology • Previous Articles     Next Articles

Cryptochrome‐mediated hypocotyl phototropism was regulated antagonistically by gibberellic acid and sucrose in Arabidopsis

Qing-Ping Zhao, Jin-Dong Zhu, Nan-Nan Li, Xiao-Nan Wang, Xiang Zhao* and Xiao Zhang*   

  1. Key laboratory of Plant Stress Biology, State Key Laboratory of Cotton Biology, School of Life Sciences, Henan University, Kaifeng 475004, China

    *Correspondences:
    Email: Xiang Zhao (xzhao@henu.edu.cn; Dr. Zhao is fully responsible for the distribution of all materials associated with this article); Xiao Zhang (xzhang@henu.edu.cn).
  • Received:2019-01-24 Accepted:2019-03-27 Online:2019-04-02 Published:2020-05-01

Abstract:

Both phototropins (phot1 and phot2) and cryptochromes (cry1 and cry2) were proven as the Arabidopsis thaliana blue light receptors. Phototropins predominately function in photomovement, and cryptochromes play a role in photomorphogenesis. Although cryptochromes have been proposed to serve as positive modulators of phototropic responses, the underlying mechanism remains unknown. Here, we report that depleting sucrose from the medium or adding gibberellic acids (GAs) can partially restore the defects in phototropic curvature of the phot1 phot2 double mutants under high‐intensity blue light; this restoration does not occur in phot1 phot2 cry1 cry2 quadruple mutants and nph3 (nonphototropic hypocotyl 3) mutants which were impaired phototropic response in sucrose‐containing medium. These results indicate that GAs and sucrose antagonistically regulate hypocotyl phototropism in a cryptochromes dependent manner, but it showed a crosstalk with phototropin signaling on NPH3. Furthermore, cryptochromes activation by blue light inhibit GAs synthesis, thus stabilizing DELLAs to block hypocotyl growth, which result in the higher GAs content in the shade side than the lit side of hypocotyl to support the asymmetric growth of hypocotyl. Through modulation of the abundance of DELLAs by sucrose depletion or added GAs, it revealed that cryptochromes have a function in mediating phototropic curvature.

The concluded function of cryptochromes in hypocotyls phototropism is controversial. By phenotypic analysis of mutant lines grown on sucrose free medium or medium with added gibberellic acids, we demonstrated that cryptochromes-mediated hypocotyl phototropism was regulated antagonistically by gibberellin and sugar. This process showed a crosstalk with phototropin signaling on NPH3.
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