Post-Doctoral researcher Utrecht University, department of biology, Plant Ecofysiology
Plants compete for light by growing taller than their nearest competitors. This is called the shade avoidance response and it is regulated by an increase of Far-Red light (FR) reflected from neighbouring leaves. The root responds to this shoot-sensed FR cue as well, by reducing lateral root emergence. It has been known for a long time that the plant hormone Gibberellic Acid (GA) is involved in FR-induced shoot elongation. GA is also transported from shoot to root, however, it’s role in regulating lateral root growth is unclear. We discovered GA is also involved in the response of the root system to shoot-sensed FR light. GA manipulations, both chemical and genetic, can modulate the lateral root reduction induced by shoot FR. Using the latest FRET-based GA biosensor GPS1, we were able to observe detailed GA responses in the root upon shoot FR illumination and visualize GA transport. The regulatory role of GA root growth appears to be both parallel to and dependent upon the role of root-shoot mobile HY5, a light-responsive transcription factor. Both GA and HY5 are transported rootwards and interact in the shoot and root. Our data show a new way in which hormonal and protein signaling coordinate development across spatial scales by adjusting (lateral) root growth from above-ground FR light signals.