Phytochrome-regulated repression of gene expression requires calcium and cGMP

EMBO J. 1997 May 15;16(10):2554-64. doi: 10.1093/emboj/16.10.2554.


The plant photoreceptor phytochrome A utilizes three signal transduction pathways, dependent upon calcium and/or cGMP, to activate genes in the light. In this report, we have studied the phytochrome A regulation of a gene that is down-regulated by light, asparagine synthetase (AS1). We show that AS1 is expressed in the dark and repressed in the light. Repression of AS1 in the light is likely controlled by the same calcium/cGMP-dependent pathway that is used to activate other light responses. The use of the same signal transduction pathway for both activating and repressing different responses provides an interesting mechanism for phytochrome action. Using complementary loss- and gain-of-function experiments we have identified a 17 bp cis-element within the AS1 promoter that is both necessary and sufficient for this regulation. This sequence is likely to be the target for a highly conserved phytochrome-generated repressor whose activity is regulated by both calcium and cGMP.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aspartate-Ammonia Ligase / biosynthesis*
  • Aspartate-Ammonia Ligase / genetics
  • Calcium / metabolism*
  • Cyclic GMP / metabolism*
  • Darkness
  • Down-Regulation
  • Gene Expression Regulation, Plant*
  • Genes, Reporter
  • Glucuronidase / biosynthesis
  • Glucuronidase / genetics
  • Light
  • Lycopersicon esculentum / radiation effects
  • Morphogenesis / radiation effects
  • Phytochrome / metabolism
  • Phytochrome / radiation effects*
  • Phytochrome A
  • Promoter Regions, Genetic
  • Recombinant Fusion Proteins / biosynthesis
  • Signal Transduction


  • Phytochrome A
  • Recombinant Fusion Proteins
  • Phytochrome
  • Glucuronidase
  • Aspartate-Ammonia Ligase
  • Cyclic GMP
  • Calcium