Shoot to root transport of the HY5 transcription factor drives root developmental plasticity under neighbour shade.
- 1Heidelberg University - Centre for Organismal Studies
Abstract
Plants perceive competitors through the reflection of Far-Red light from neighbouring leaves. A decrease in the Red: Far-red light ratio (R:FR) is perceived by phytochrome photoreceptors and triggers elongation responses aboveground, allowing plants to anticipate future competition for light; their primary energy source. However, low R:FR perception by the shoot also prompts an alteration of root development, possibly to conserve resources. An important regulator of this response is the bZIP transcription factor ELONGATED HYPOCOTYL 5 (HY5), which can be transported from the shoot to the root, where it suppresses auxin signaling and lateral root outgrowth. However, it remains unknown whether HY5 transport is the direct link between shoot-perceived low R:FR and a decrease in lateral root outgrowth. We therefore sought to uncover the mechanics and speed of HY5 transport. To this end, we constructed shoot-specific inducible lines to perform live-imaging of HY5 transport using a vertical confocal microscope. This allowed us to follow the transport and unloading of HY5 from the phloem into the protophloem pericycle, where it becomes nuclearly localized, in real time over a 24-hour period. To mimic plant competition, we applied supplemental FR light and observed that this increased the HY5 protein levels in the shoot and subsequent HY5 protein transport from shoot-to-root. Finally, we were able to show that shoot-expressed HY5 is necessary and sufficient to induce the root response to shoot perceived Far-Red light. This work showcases in detail how a small general transcription factor functions as a long-distance signal between shoot and root and integrates environmental signalling over long distances in the plant.
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BibTeX
@misc{velde2026shoot,
title = {{Shoot to root transport of the HY5 transcription factor drives root developmental plasticity under neighbour shade.}},
author = {K. van der Velde and A. Ali and V. Hoogers and F. Stamm and A. Patnaik and O. Heliel and D. Rietveld and T. Akyuz and K. Retzer and J. Petrasek and R. Pierik and K. van Gelderen},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.18.759902},
url = {https://www.biorxiv.org/content/10.64898/2026.10.18.759902v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Shoot to root transport of the HY5 transcription factor drives root developmental plasticity under neighbour shade.
AU - K. van der Velde
AU - A. Ali
AU - V. Hoogers
AU - F. Stamm
AU - A. Patnaik
AU - O. Heliel
AU - D. Rietveld
AU - T. Akyuz
AU - K. Retzer
AU - J. Petrasek
AU - R. Pierik
AU - K. van Gelderen
PY - 2026
DA - 2026/10/18
PB - bioRxiv
DO - 10.64898/2026.10.18.759902
UR - https://www.biorxiv.org/content/10.64898/2026.10.18.759902v1
AB - Plants perceive competitors through the reflection of Far-Red light from neighbouring leaves. A decrease in the Red: Far-red light ratio (R:FR) is perceived by phytochrome photoreceptors and triggers elongation responses aboveground, allowing plants to anticipate future competition for light; their primary energy source. However, low R:FR perception by the shoot also prompts an alteration of root development, possibly to conserve resources. An important regulator of this response is the bZIP transcription factor ELONGATED HYPOCOTYL 5 (HY5), which can be transported from the shoot to the root, where it suppresses auxin signaling and lateral root outgrowth. However, it remains unknown whether HY5 transport is the direct link between shoot-perceived low R:FR and a decrease in lateral root outgrowth. We therefore sought to uncover the mechanics and speed of HY5 transport. To this end, we constructed shoot-specific inducible lines to perform live-imaging of HY5 transport using a vertical confocal microscope. This allowed us to follow the transport and unloading of HY5 from the phloem into the protophloem pericycle, where it becomes nuclearly localized, in real time over a 24-hour period. To mimic plant competition, we applied supplemental FR light and observed that this increased the HY5 protein levels in the shoot and subsequent HY5 protein transport from shoot-to-root. Finally, we were able to show that shoot-expressed HY5 is necessary and sufficient to induce the root response to shoot perceived Far-Red light. This work showcases in detail how a small general transcription factor functions as a long-distance signal between shoot and root and integrates environmental signalling over long distances in the plant.
ER -