Hyo-Jun Lee1,*, Jun-Ho Ha1,*, Sang-Gyu Kim2,3,*, Han-Kyu Choi1, Zee Hwan Kim1, Yun-Jeong Han4, Jeong-Il Kim4, Youngjoo Oh3, Variluska Fragoso3, Kwangsoo Shin5,6, Taeghwan Hyeon5,6, Hong-Gu Choi7, Kyung-Hwan Oh7, Ian T. Baldwin3,†, and Chung-Mo Park1,8,†
1Department of Chemistry, Seoul National University, Seoul 08826, Korea.
2Center for Genome Engineering, Institute for Basic Science, Daejeon 34047, Korea.
3Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Jena 07745, Germany.
4Department of Biotechnology and Kumho Life Science Laboratory, Chonnam National University, Gwangju 61186, Korea.
5Center for Nanoparticle Research, Institute for Basic Science, Seoul 08826, Korea.
6School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Korea.
7Department of Physics, Yonsei University, Seoul 03722, Korea.
8Plant Genomics and Breeding Institute, Seoul National University, Seoul 08826, Korea.
†Corresponding author. Chung-Mo Park, Ian T. Baldwin
* These authors contributed equally to this work.
The roles of photoreceptors and their associated signaling mechanisms have been extensively studied in plant photomorphogenesis with a major focus on the photoresponses of the shoot system. Accumulating evidence indicates that light also influences root growth and development through the light-induced release of signaling molecules that travel from the shoot to the root. We explored whether aboveground light directly influences the root system of Arabidopsis thaliana. Light was efficiently conducted through the stems to the roots, where photoactivated phytochrome B (phyB) triggered expression of ELONGATED HYPOCOTYL 5 (HY5) and accumulation of HY5 protein, a transcription factor that promotes root growth in response to light. Stimulation of HY5 in response to illumination of only the shoot was reduced when root tissues carried a loss-of-function mutation in PHYB, and HY5 mutant roots exhibited alterations in root growth and gravitropism in response to shoot illumination. These findings demonstrate that the underground roots directly sense stem-piped light to monitor the aboveground light environment during plant environmental adaptation.