The plant hormone indole-3 acetic acid (IAA or auxin) controls many aspects of plant development, including the production of lateral roots1,2,3. Ubiquitin-mediated proteolysis has a central role in this process. The genes AXR1 and TIR1 aid the assembly of an active SCF (Skp1/Cullin/F-box) complex that probably promotes degradation of the AUX/IAA transcriptional repressors in response to auxin4,5,6,7,8. The transcription activator NAC1, a member of the NAM/CUC family of transcription factors, functions downstream of TIR1 to transduce the auxin signal for lateral root development9. Here we show that SINAT5, an Arabidopsis homologue of the RING-finger Drosophila protein SINA, has ubiquitin protein ligase activity and can ubiquitinate NAC1. This activity is abolished by mutations in the RING motif of SINAT5. Overexpressing SINAT5 produces fewer lateral roots, whereas overexpression of a dominant-negative Cys49 → Ser mutant of SINAT5 develops more lateral roots. These lateral root phenotypes correlate with the expression of NAC1 observed in vivo. Low expression of NAC1 in roots can be increased by treatment with a proteasome inhibitor, which indicates that SINAT5 targets NAC1 for ubiquitin-mediated proteolysis to downregulate auxin signals in plant cells.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
del Pozo, J. C., Timpte, C., Tan, S., Callis, J. & Estelle, M. The ubiquitin-related protein RUB1 and auxin response in Arabidopsis. Science 280, 1760–1763 (1998)
Ruegger, M. et al. The TIR1 protein of Arabidopsis functions in auxin response and is related to human SKP2 and yeast grr1p. Genes Dev. 12, 198–207 (1998)
Rogg, L. E., Lasswell, J. & Bartel, B. A gain-of-function mutation in IAA28 suppresses lateral root development. Plant Cell 13, 465–480 (2001)
Ouellet, F., Overvoorde, P. J. & Theologis, A. IAA17/AXR3: biochemical insight into an auxin mutant phenotype. Plant Cell 13, 829–841 (2001)
Gray, W. M. et al. Identification of an SCF ubiquitin-ligase complex required for auxin response in Arabidopsis thaliana. Genes Dev. 13, 1678–1691 (1999)
Gray, W. M., Kepinski, S., Rouse, D., Leyser, O. & Estelle, M. Auxin regulates SCF(TIR1)-dependent degradation of AUX/IAA proteins. Nature 414, 271–276 (2001)
Ramos, J. A., Zenser, N., Leyser, O. & Callis, J. Rapid degradation of auxin/indoleacetic acid proteins requires conserved amino acids of domain II and is proteasome dependent. Plant Cell. 13, 2349–2360 (2001)
Zenser, N., Ellsmore, A., Leasure, C. & Callis, J. Auxin modulates the degradation rate of Aux/IAA proteins. Proc. Natl Acad. Sci. USA 98, 11795–11800 (2001)
Xie, Q., Frugis, G., Colgan, D. & Chua, N. H. Arabidopsis NAC1 transduces auxin signal downstream of TIR1 to promote lateral root development. Genes Dev. 14, 3024–3036 (2000)
Carthew, R. W. & Rubin, G. M. Seven in absentia, a gene required for specification of R7 cell fate in the Drosophila eye. Cell 63, 561–577 (1990)
Nemani, M. et al. Activation of the human homologue of the Drosophila sina gene in apoptosis and tumour suppression. Proc. Natl Acad. Sci. USA 93, 9039–9342 (1996)
Hu, G. & Fearon, E. R. Siah-1 N-terminal RING domain is required for proteolysis function, and C-terminal sequences regulate oligomerization and binding to target proteins. Mol. Cell. Biol. 19, 724–732 (1999)
Polekhina, G. et al. Siah ubiquitin ligase is structurally related to TRAF and modulates TNF-α signaling. Nature Struct. Biol. 9, 68–75 (2002)
Lorick, K. L. et al. RING fingers mediate ubiquitin-conjugating enzyme (E2)-dependent ubiquitination. Proc. Natl Acad. Sci. USA 96, 11364–11369 (1999)
Joazeiro, C. A. et al. The tyrosine kinase negative regulator c-Cbl as a RING-type, E2 dependent ubiquitin-protein ligase. Science 286, 309–312 (1999)
Fang, S., Jensen, J. P., Ludwig, R. L., Vousden, K. H. & Weissman, A. M. Mdm2 is a RING finger-dependent ubiquitin protein ligase for itself and p53. J. Biol. Chem. 275, 8945–8951 (2000)
Li, S., Li, Y., Carthew, R. W. & Lai, Z. C. Photoreceptor cell differentiation requires regulated proteolysis of the transcriptional repressor Tramtrack. Cell. 90, 469–478 (1997)
Hu, G. et al. Mammalian homologs of seven in absentia regulate DCC via the ubiquitin-proteasome pathway. Genes Dev. 11, 2701–2747 (1997)
Tiedt, R., Bartholdy, B. A., Matthias, G., Newell, J. W. & Matthias, P. The RING finger protein Siah-1 regulates the level of the transcriptional coactivator OBF-1. EMBO J. 20, 4143–4152 (2001)
Boehm, J., He, Y., Greiner, A., Staudt, L. & Wirth, T. Regulation of BOB.1/OBF.1 stability by SIAH. EMBO J. 20, 4153–4162 (2001)
Nie, J. et al. LNX functions as a RING type E3 ubiquitin ligase that targets the cell fate determinant Numb for ubiquitin-dependent degradation. EMBO J. 21, 93–102 (2002)
Susini, L. et al. Siah-1 binds and regulates the function of Numb. Proc. Natl Acad. Sci. USA 98, 15067–15072 (2001)
Matsuzawa, S. & Reed, J. C. Siah-1 SIP and Ebi collaborate in a novel pathway for β-catenin degradation linked to p53 responses. Mol. Cell 7, 915–926 (2001)
Liu, J. et al. Siah-1 mediates a novel β-catenin degradation pathway linking p53 to the adenomatous polyposis coli protein. Mol. Cell 7, 927–936 (2001)
Hashizume, R. et al. A RING heterodimer BRCA1–BARD1 is a ubiquitin ligase inactivated by a breast cancer-derived mutation. J. Biol. Chem. 276, 14537–14540 (2001)
Xie, Q., Sanz-Burgos, A. P., Guo, H., Garcia, J. A. & Gutierrez, C. GRAB proteins, novel members of the NAC domain family, isolated by their interaction with a geminivirus protein. Plant Mol. Biol. 39, 647–656 (1999)
Kost, B., Spielhofer, P. & Chua, N. H. A GFP-mouse talin fusion protein labels plant actin filaments in vivo and visualizes the actin cytoskeleton in growing pollen tubes. Plant J. 16, 393–401 (1998)
Clough, S. J. & Bent, A. F. Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. Plant J. 16, 735–743 (1998)
We thank E. Ng and W.-P. Tang for technical assistance; Y.-S. Chan for taking the GUS pictures; and P. Hare for reading the manuscript. This work was supported in part by a grant from the NIH to N.-H.C. This work was initiated in the Institute of Molecular Agrobiology, Singapore, supported by Singapore A-star funding.
The authors declare that they have no competing financial interests.
About this article
Cite this article
Xie, Q., Guo, H., Dallman, G. et al. SINAT5 promotes ubiquitin-related degradation of NAC1 to attenuate auxin signals. Nature 419, 167–170 (2002) doi:10.1038/nature00998
Auxin abolishes SHI ‐ RELATED SEQUENCE 5‐mediated inhibition of lateral root development in Arabidopsis
New Phytologist (2020)
Genome-wide association and transcriptional studies reveal novel genes for unsaturated fatty acid synthesis in a panel of soybean accessions
BMC Genomics (2019)
An Integrated Transcriptome and Proteome Analysis Reveals Putative Regulators of Adventitious Root Formation in Taxodium ‘Zhongshanshan’
International Journal of Molecular Sciences (2019)
RNAseq analysis reveals drought-responsive molecular pathways with candidate genes and putative molecular markers in root tissue of wheat
Scientific Reports (2019)
Biological Research (2019)