Strigolactone and cytokinin act antagonistically in regulating rice mesocotyl elongation in darkness

Plant Cell Physiol. 2014 Jan;55(1):30-41. doi: 10.1093/pcp/pct150. Epub 2013 Oct 21.


Strigolactones (SLs) are a group of phytohormones that control plant growth and development including shoot branching. Previous studies of the phenotypes of SL-related rice (Oryza sativa) dwarf (d) mutants demonstrated that SLs inhibit mesocotyl elongation by controlling cell division. Here, we found that the expression of cytokinin (CK)-responsive type-A RESPONSE REGULATOR (RR) genes was higher in d10-1 and d14-1 mutants than in the wild type. However, CK levels in mesocotyls of the d mutants were not very different from those in the wild type. On the other hand, application of a synthetic CK (kinetin) enhanced mesocotyl elongation in the d mutants and the wild type. d10-1 and d14-1 mesocotyls were more sensitive to CK than wild-type mesocotyls, suggesting that the up-regulation of the CK-responsive type-A RR genes and the higher elongation of mesocotyls in the d mutants are mainly due to the increased sensitivity of the d mutants to CK. Co-treatment with kinetin and a synthetic SL (GR24) confirmed the antagonistic functions of SL and CK on mesocotyl elongation. OsTCP5, which encodes a transcription factor belonging to the cell division-regulating TCP family, was also regulated by SL and CK and its expression was negatively correlated with mesocotyl length. These findings suggest that OsTCP5 contributes to the SL- and CK-controlled mesocotyl elongation in darkness.

Keywords: Cytokinin; Mesocotyl; Rice; Strigolactone.

MeSH terms

  • Cotyledon / growth & development*
  • Cytokinins / pharmacology*
  • Darkness*
  • Gene Expression Regulation, Plant / drug effects
  • Kinetin / pharmacology
  • Lactones / pharmacology*
  • Mutation / genetics
  • Oryza / drug effects*
  • Oryza / genetics
  • Oryza / growth & development*
  • Up-Regulation / drug effects
  • Up-Regulation / genetics


  • Cytokinins
  • GR24 compound
  • Lactones
  • Kinetin