Hd1,a CONSTANS ortholog in rice, functions as an Ehd1 repressor through interaction with monocot-specific CCT-domain protein Ghd7

Plant J. 2016 May;86(3):221-33. doi: 10.1111/tpj.13168.


Flowering time is an important agronomic trait that affects crop yields. In cereals, several CCT-domain proteins unique to monocots, such as Grain number, plant height, and heading date 7 (Ghd7) gene, have been identified as key floral repressors, although the corresponding molecular mechanisms have been unknown until now. In rice, a short-day plant, Heading date 1 (Hd1) gene, a rice ortholog of Arabidopsis floral activator CONSTANS (CO), represses flowering under non-inductive long-day (LD) conditions and induces it under inductive short-day (SD) conditions. Here, we report biological interactions between Ghd7 and Hd1, which together repress Early heading date 1 (Ehd1), a key floral inducer under non-inductive LD conditions. In addition to this genetic interaction between them, Co-IP experiments further demonstrated that a Ghd7-Hd1 protein formed a complex in vivo and ChIP and luciferase reporter analyses suggested that this complex specifically binds to a cis-regulatory region in Ehd1 and represses its expression. These findings imply that Hd1, an evolutionally conserved transcriptional activator, can function as a strong transcriptional repressor within a monocot-specific flowering-time pathway through with Ghd7.

Keywords: flowering time; monocot-specific pathway; repressor complex; rice.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Down-Regulation
  • Flowers / genetics
  • Flowers / growth & development
  • Flowers / metabolism
  • Gene Expression Regulation, Plant*
  • Oryza / genetics
  • Oryza / metabolism*
  • Oryza / physiology
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Plant Proteins / physiology*
  • Protein Domains
  • RNA, Messenger / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription Factors / physiology*


  • Plant Proteins
  • RNA, Messenger
  • Transcription Factors