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Schriftzug Angewandte Genetik Collage von Motiven der Angewandten Genetik

Dahlem Research School

Member of Dahlem Centre of Plant Sciences (DCPS)

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Research group Johansson

Research interests

Light as an external signal has been shown to control many aspects of plant growth and development throughout the plant lifecycle including germination, de-etiolation, shade avoidance, chloroplast movements, phototropism, entrainment of the circadian clock and time of flowering. The seedling de-etiolation is one of the most dramatic response to any single external stimuli in nature and as such, it is not surprising that this response affects a large proportion of the plant transcriptome. This is largely mediated by the red and blue light receptors (phytochromes and cryptochromes). However, these photoreceptors do not regulate transcription directly but via a complex network of positive and negative factors of photomorphogenesis.

Over two decades ago, COP1 was identified as a major negative regulator of light signalling through its photomorphogenic phenotype in darkness. In the dark, COP1 acts as an E3 ubiquitin ligase targeting several positive factors of photomorphogenesis for degradation, most notably the bZIP transcription factor HY5. Upon light irradiation, COP1 activity is inhibited by the photoreceptors in addition to being excluded from the nucleus resulting in the accumulation of HY5 and consequently de-etiolation.

Fluence response of light signaling mutants
Photograph of seedlings grown for 7 days in darkness or increasing amounts of red light. Increasing light levels results in opening and expansion of the cotyledons, inhibition of hypocotyl elongation and chlorophyll accumulation. The hy5 mutant is hyposensitive to light while the cop1 mutant is photomorphogenic in darkness.

In the Johansson group we are interested in the molecular events taking place between the perception of light by the photoreceptors and the following transcriptional response during de-etiolation. We are working with a group of B-Box zinc finger proteins that physically interact with COP1 and/or HY5. As predicted by these interactions, these B-Box proteins do indeed modulate the light signalling pathway as manifested in the mutants by altered inhibition of hypocotyl elongation and accumulation of anthocyanin. Currently, we are examining the similarities and differences between these B-Box proteins and are working towards the mechanism by which they alter HY5 action.



Johansson H, Zeidler M. (2016) Automatic chloroplast movement analysis. Methods Mol. Biol. 1398, 29-35.

Johansson H, Hughes J. (2014) Nuclear phytochrome B regulates leaf flattening through phytochrome interacting factors. Mol. Plant 7, 1693-1696.

Johansson H*, Jones JH*, Foreman J, Hemsted H, Stewart K, Grima R, Halliday KJ. (2014) Arabidopsis cell expansion is controlled by a photothermal switch. Nat. Commun. 5, 4848.

Toledo-Ortiz G, Johansson H, Lee KP, Bou-Torrent J, Stewart K, Steel G, Rodríguez-Concepción M, Halliday KJ. (2014) The HY5-PIF regulatory module coordinates light and temperature control of photosynthetic gene transcription. PLoS Genet. 10, e1004416.

Gangappa SN, Crocco CD, Johansson H, Datta S, Hettiarachchi C, Holm M, Botto JF. (2013) The Arabidopsis B-BOX protein BBX25 interacts with HY5, negatively regulating BBX22 expression to suppress seedling photomorphogenesis. Plant Cell 25, 1243-1257.

Foreman J*, Johansson H*, Hornitschek P, Josse E-M, Fankhauser C, Halliday KJ. (2011) Light receptor action is critical for maintaining plant biomass at warm ambient temperatures. Plant J. 65, 441-452.

Datta S*, Johansson H*, Hettiarachchi C, Irigoyen ML, Desai M, Rubio V, Holm M. (2008) LZF1/SALT TOLERANCE HOMOLOG3, an Arabidopsis B-box protein involved in light-dependent development and gene expression, undergoes COP1-mediated ubiquitination. Plant Cell 20, 2324-2338.

Datta S, Johansson H, Hettiarachchi C, Holm M. (2008) STH2 has 2 B there: An insight into the role of B-box containing proteins in Arabidopsis. Plant Signal Behav. 3, 547-548.

Datta S, Hettiarachchi C, Johansson H, Holm M. (2007) SALT TOLERANCE HOMOLOG2, a B-box protein in Arabidopsis that activates transcription and positively regulates light-mediated development. Plant Cell 19, 3242-3255.


New publication

A review article about a novel type of stress in plants caused by alteration of the photoperiod has been published in Trends in Plant Science.
September 2017

New publication

An article about the analysis of a cytokinin-responsive gene of Arabidopsis thaliana encoding a novel F-box protein regulating sterol biosynthesis has been published in Journal of Experimental Botany.
May 2017

New publication

A report about constitutively active mutants of the cytokinin receptors AHK2 und AHK3 and their impact on organ size, flowering time, and plant longevity has been published in Plant Physiology.
March 2017

New publication

An article about the role of the transcription factor ERF105 in freezing tolerance and cold acclimation has been published in Plant Cell and Environment.
January 2017
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Updated: 2017-10-04