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

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


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.

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

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis / radiation effects*
  • Arabidopsis Proteins / metabolism*
  • Flowers / physiology
  • Flowers / radiation effects
  • Gene Expression Regulation, Plant / radiation effects
  • Light*
  • Mesophyll Cells / cytology
  • Mesophyll Cells / metabolism
  • Morphogenesis / radiation effects*
  • Organ Specificity* / radiation effects
  • Phenotype
  • Phototropism
  • Phytochrome A / metabolism*
  • Plant Stomata / cytology
  • Plant Stomata / metabolism
  • Plants, Genetically Modified
  • Proteolysis / radiation effects
  • Recombinant Fusion Proteins / metabolism
  • Seedlings / metabolism
  • Signal Transduction / radiation effects*
  • Transcription, Genetic / radiation effects


  • Arabidopsis Proteins
  • PHYA protein, Arabidopsis
  • Phytochrome A
  • Recombinant Fusion Proteins