Auxin modulates the degradation rate of Aux/IAA proteins

These results suggest that auxin rapidly modulates the degradation rate of Auxinindole-3-acetic acid protein proteins, with higher levels of auxin increasing the proteolytic rate of AuxIAA family members

N. Zenser; A. Ellsmore; C. Leasure; J. Callis


Scholarcy highlights

  • Auxin is a classic phytohormone involved in a myriad of developmental and environmental processes: embryo patterning, cell division and elongation, vascular differentiation, lateral root initiation, gravitropism, and phototropism
  • We previously demonstrated that LUC translational fusions with the Arabidopsis Auxinindole-3-acetic acid protein protein IAA1 or the pea AuxIAA protein PSIAA6 are enzymatically active and rapidly degraded in transgenic Arabidopsis plants
  • We demonstrate here that exogenous auxin increased the degradation rate of AuxIAA::LUC proteins, resulting in a decrease in AuxIAA::LUC activity and protein
  • We hypothesize that the response of endogenous AuxIAA proteins to auxin is identical to that observed here for introduced AuxIAA::LUC proteins, and we hypothesize further that endogenous auxin are capable of modulating AuxIAA degradation rates
  • Given the importance of AuxIAA proteins in auxin signaling as revealed by genetic screens, modulation of AuxIAA abundance by auxin could be an important point of control for downstream auxin-regulated events
  • No differences in the timing of the auxin response between TIR1 and tir were seen
  • Whether all AuxIAA family members respond to exogenous auxin is currently unknown; we demonstrated that the protein degradation rates of two different full-length AuxIAA::LUC fusions are auxin responsive
  • Auxin could theoretically increase Auxinindole-3-acetic acid protein proteolysis by altering: the SCF-activation state through RUB addition or other modification; COP9 signalosome activityinteraction with SCF; andor Aux IAA modification

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