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Nat Commun. 2018 Jun 19;9(1):2403. doi: 10.1038/s41467-018-04752-1.

A phosphorylation switch turns a positive regulator of phototropism into an inhibitor of the process.

Author information

1
Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Genopode Building, 1015, Lausanne, Switzerland.
2
Department of Botany and Plant Biology, University of Geneva, 1211, Geneva 4, Switzerland.
3
Protein Analysis Facility, Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015, Lausanne, Switzerland.
4
Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Genopode Building, 1015, Lausanne, Switzerland. christian.fankhauser@unil.ch.

Abstract

Phototropins are light-activated protein kinases, which contribute to photosynthesis optimization both through enhancement of photon absorption when light is limiting and avoidance responses in high light. This duality is in part endowed by the presence of phototropins with different photosensitivity (phot1 and phot2). Here we show that phot1, which senses low light to promote positive phototropism (growth towards the light), also limits the response in high light. This response depends in part on phot1-mediated phosphorylation of Phytochrome Kinase Substrate 4 (PKS4). This light-regulated phosphorylation switch changes PKS4 from a phototropism enhancer in low light to a factor limiting the process in high light. In such conditions phot1 and PKS4 phosphorylation prevent phototropic responses to shallow light gradients and limit phototropism in a natural high light environment. Hence, by modifying PKS4 activity in high light the phot1-PKS4 regulon enables appropriate physiological adaptations over a range of light intensities.

PMID:
29921904
PMCID:
PMC6008296
DOI:
10.1038/s41467-018-04752-1
[Indexed for MEDLINE]
Free PMC Article

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