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

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.

Phototropin 1 Mediates High-Intensity Blue Light-Induced Chloroplast Accumulation Response in a Root Phototropism 2-Dependent Manner in Arabidopsis phot2 Mutant Plants

“…Previously, the expression of PHOT2 in mature leaves was shown to be significantly induced by high light irradiation (Labuz et al, 2012 ). We also found that RPT2 expression significantly increased with increasing BL intensity (Zhao et al, 2020 ). Both KAC1 and PMI2 have been shown to be important for the regulation of chloroplast movement, although the underlying mechanisms of their functions are still unclear (Luesse et al, 2006 ; Suetsugu et al, 2010 ).…”

A PSTAIRE-type cyclin-dependent kinase controls light responses in land plants

“…In a nonmutually exclusive alternative, redundant pathways for hypocotyl phototropism have been suggested in Arabidopsis (45), in which AtCDKA;1 may participate. Further studies on AtCDKA;1 function in Arabidopsis will extend our understanding of the mechanisms underlying light responses in land plants.…”

Cryptochromes are the dominant photoreceptors mediating heliotropic responses of Arabidopsis inflorescences

“…The presence of phytochromes and the blue light photoreceptors cryptochromes in the nucleus regulates the expression of several genes that indirectly contribute to modulate phototropic responses (reviewed by Goyal, Szarzynska, & Fankhauser, 2013; Liscum et al, 2014). In this context, several studies indicate that cryptochromes positively regulate the blue‐light mediated phototropism in etiolated seedlings (Kang, Lian, Wang, Huang, & Yang, 2009; Nagashima et al, 2008; Ohgishi, Saji, Okada, & Sakai, 2004; Tsuchida‐Mayama et al, 2010; Zhao et al, 2019). Moreover, the behaviour of phyA cry1 cry2 loss‐of‐function mutants suggests that both phyA and cryptochromes are required, to some extent, for the phototropic response (Tsuchida‐Mayama et al, 2010).…”