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New Phytol. 2016 Jul;211(2):584-98. doi: 10.1111/nph.13941. Epub 2016 Mar 30.

Characterization of photomorphogenic responses and signaling cascades controlled by phytochrome-A expressed in different tissues.

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Faculty of Biology, Institute of Molecular Plant Physiology, University of Freiburg, Schänzlestrasse 1, D-79104, Freiburg, Germany.
Institute of Plant Biology, Biological Research Centre, Temesvári krt.62, Szeged, H-6726, Hungary.
Institute of Biophysics, Biological Research Centre, Temesvári krt.62, Szeged, H-6726, Hungary.
BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, 79104, Germany.
Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JH, UK.


The photoreceptor phytochrome A acts as a light-dependent molecular switch and regulates responses initiated by very low fluences of light (VLFR) and high fluences (HIR) of far-red light. PhyA is expressed ubiquitously, but how phyA signaling is orchestrated to regulate photomorphogenesis is poorly understood. To address this issue, we generated transgenic Arabidopsis thaliana phyA-201 mutant lines expressing the biologically active phyA-YFP photoreceptor in different tissues, and analyzed the expression of several reporter genes, including ProHY5:HY5-GFP and Pro35S:CFP-PIF1, and various FR-HIR-dependent physiological responses. We show that phyA action in one tissue is critical and sufficient to regulate flowering time and root growth; control of cotyledon and hypocotyl growth requires simultaneous phyA activity in different tissues; and changes detected in the expression of reporters are not restricted to phyA-containing cells. We conclude that FR-HIR-controlled morphogenesis in Arabidopsis is mediated partly by tissue-specific and partly by intercellular signaling initiated by phyA. Intercellular signaling is critical for many FR-HIR induced responses, yet it appears that phyA modulates the abundance and activity of key regulatory transcription factors in a tissue-autonomous fashion.


Arabidopsis thaliana; photomorphogenesis; phytochrome A; signaling; tissue/cell specificity; transcription

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