Interdependency of Brassinosteroid and Auxin Signaling in Arabidopsis

We describe a shared auxin:BR pathway required for seedling growth

Jennifer L Nemhauser; Todd C Mockler; Joanne Chory

2004

Scholarcy highlights

  • The continuous shaping of plant form is a marvel of signal integration
  • Several lines of evidence suggested that auxin:BR synergism did not depend upon biosynthetic regulation of hormone levels; rather, the two response pathways are likely to converge at the promoters of shared target genes
  • Increased temperature has been demonstrated previously to be an effective method of altering auxin levels in the shoot and leads to robust increases in hypocotyl length
  • We used a heat shock–inducible b-glucuronidase reporter fused to the N-terminal portion of AXR3 described by Gray and colleagues. This construct was rapidly turned over in the presence of auxin but showed no change in stability following BR treatment. These results suggested that the interaction between the auxin and BR pathways was likely at the promoters of shared target genes
  • Physiological and genetic evidence suggests that auxin, GAs, and ethylene promote hypocotyl growth by largely independent means
  • BRs and GAs interact additively in most cell elongation bioassays, and analysis of bri1 mutants suggests that the two hormones independently and antagonistically regulate transcription of some target genes
  • Higher-order interactions among several transcription factor complexes, perhaps directly involving members of the BES1/BZR1 family, could provide additional control of the shared auxin:BR response pathway

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