Plant Development Is Regulated by a Family of Auxin Receptor F Box Proteins

Abstract

The plant hormone auxin has been implicated in virtually every aspect of plant growth and development. Auxin acts by promoting the degradation of transcriptional regulators called Aux/IAA proteins. Aux/IAA degradation requires TIR1, an F box protein that has been shown to function as an auxin receptor. However, loss of TIR1 has a modest effect on auxin response and plant development. Here we show that three additional F box proteins, called AFB1, 2, and 3, also regulate auxin response. Like TIR1, these proteins interact with the Aux/IAA proteins in an auxin-dependent manner. Plants that are deficient in all four proteins are auxin insensitive and exhibit a severe embryonic phenotype similar to the mp/arf5 and bdl/iaa12 mutants. Correspondingly, all TIR1/AFB proteins interact with BDL, and BDL is stabilized in triple mutant plants. Our results indicate that TIR1 and the AFB proteins collectively mediate auxin responses throughout plant development.

Strigolactone Acts Downstream of Auxin to Regulate Bud Outgrowth in Pea and Arabidopsis

“…This implies that the auxin response mutants may branch, at least in part, due to endogenous strigolactone depletion and that auxin response is not necessarily required for strigolactone to inhibit shoot branching. The reduced branching in GR24-treated tir1 afb1 afb2 afb3 quadruple mutant plants suggests that AXR1 regulation of strigolactone biosynthesis might be mediated by the SCF TIR1/AFB ubiquitin ligase complex, which functions as an auxin receptor and targets proteins for ubiquitination (Dharmasiri et al, 2005a(Dharmasiri et al, , 2005bKepinski and Leyser, 2005). Therefore, we propose that one role for auxin in mediating apical dominance is through auxin inducing the expression of strigolactone biosynthesis genes (Fig.…”

“…To further investigate the relationship between auxin response and shoot branching, axr1 and tir1 afb1 afb2 afb3 quadruple auxin response mutant plants (Dharmasiri et al, 2005b) were grown in plant culture trays and their shoot-branching responses to GR24 supplied to the roots in the medium were measured (Fig. 3B).…”

Peptidyl-prolyl isomerization targets rice Aux/IAAs for proteasomal degradation during auxin signalling

“…The Co-IP experiments were performed according to the previously described methods with minor modifications 57 . To prepare total cellular proteins, plant samples were grinded in liquid nitrogen, and then extracted in grinding buffer (50 mM Tris-HCl, pH 7.5, 150 mM NaCl, 10 mM MgCl 2 , 10% glycerol, 0.1% Nonidet P-40, 1 mM phenylmethylsulfonyl fluoride and 10 mM MG132).…”

Fine tuning of auxin signaling by miRNAs

“…An expanse of literature is available on the various aspects of auxin action (for recent reviews see Fleming 2006;Hartig and Beck 2006;Quint and Gray, 2006;Teale et al, 2006;Tanaka et al, 2006;Able, 2007;Spaepen et al, 2007;Vieten et al, 2007). Recent years have witnessed a tremendous leap in our understanding of the role of auxin and mechanism of its regulation (Dharmasiri et al, 2005;Woodward et al, 2005).…”