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Gene Review

NPH4  -  auxin-regulated transcriptional activator...

Arabidopsis thaliana

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Disease relevance of NPH4


High impact information on NPH4


Biological context of NPH4


Associations of NPH4 with chemical compounds

  • These characteristics of msg2 are similar to those of another auxin-insensitive mutant, non-phototropic hypocotyl4 (nph4), which is a loss-of-function mutant of AUXIN RESPONSE FACTOR7 (ARF7) (Harper et al., 2000) [8].
  • Here we show that ARF19 and ARF7 not only participate in auxin signaling, but also play a critical role in ethylene responses in Arabidopsis (Arabidopsis thaliana) roots, indicating that the ARFs serve as a cross talk point between the two hormones [5].
  • Inhibition of HDAC activity by trichostatin A also results in LR formation in the slr-1 mutant, but not in the slr-1 arf7 arf19 triple mutant, suggesting that normal HDAC activity is required for the mIAA14-mediated inactivation of ARF7/19 functions in LR initiation [9].
  • They did not undergo hypocotyl growth curvature at any of the IAA concentrations tested. msg1 is recessive and is located on chromosome 5. msg 1 hypocotyl growth is resistant to 2,4-dichlorophenoxyacetic acid (2,4-D), but the roots are as sensitive to 2,4-D as the wild type [1].
  • These LBD/ASL proteins are localized in the nucleus, and dominant repression of LBD16/ASL18 activity inhibits lateral root formation and auxin-mediated gene expression, strongly suggesting that these LBD/ASLs function downstream of ARF7- and ARF19-dependent auxin signaling in lateral root formation [10].

Other interactions of NPH4

  • The NPH4 locus encodes the auxin response factor ARF7, a conditional regulator of differential growth in aerial Arabidopsis tissue [11].
  • PICKLE is required for SOLITARY-ROOT/IAA14-mediated repression of ARF7 and ARF19 activity during Arabidopsis lateral root initiation [9].
  • Thus, NPH2 and NPH3 appear to act as signal carriers in a phototropism-specific pathway, whereas NPH4 is required for both phototropism and gravitropism and thus may function directly in the differential growth response [12].
  • Both MP and NPH4 interact strongly and selectively with themselves and with each other, and are expressed in vastly overlapping domains [13].
  • This indicated that the NPH2, NPH3, and NPH4 proteins likely function downstream of NPH1 photoactivation [12].


  1. The massugu1 mutation of Arabidopsis identified with failure of auxin-induced growth curvature of hypocotyl confers auxin insensitivity to hypocotyl and leaf. Watahiki, M.K., Yamamoto, K.T. Plant Physiol. (1997) [Pubmed]
  2. Developmental specificity of auxin response by pairs of ARF and Aux/IAA transcriptional regulators. Weijers, D., Benkova, E., Jäger, K.E., Schlereth, A., Hamann, T., Kientz, M., Wilmoth, J.C., Reed, J.W., Jürgens, G. EMBO J. (2005) [Pubmed]
  3. Functional genomic analysis of the AUXIN RESPONSE FACTOR gene family members in Arabidopsis thaliana: unique and overlapping functions of ARF7 and ARF19. Okushima, Y., Overvoorde, P.J., Arima, K., Alonso, J.M., Chan, A., Chang, C., Ecker, J.R., Hughes, B., Lui, A., Nguyen, D., Onodera, C., Quach, H., Smith, A., Yu, G., Theologis, A. Plant Cell (2005) [Pubmed]
  4. AUXIN RESPONSE FACTOR7 restores the expression of auxin-responsive genes in mutant Arabidopsis leaf mesophyll protoplasts. Wang, S., Tiwari, S.B., Hagen, G., Guilfoyle, T.J. Plant Cell (2005) [Pubmed]
  5. A role for auxin response factor 19 in auxin and ethylene signaling in Arabidopsis. Li, J., Dai, X., Zhao, Y. Plant Physiol. (2006) [Pubmed]
  6. NPH4, a conditional modulator of auxin-dependent differential growth responses in Arabidopsis. Stowe-Evans, E.L., Harper, R.M., Motchoulski, A.V., Liscum, E. Plant Physiol. (1998) [Pubmed]
  7. AUXIN RESPONSE FACTOR1 and AUXIN RESPONSE FACTOR2 regulate senescence and floral organ abscission in Arabidopsis thaliana. Ellis, C.M., Nagpal, P., Young, J.C., Hagen, G., Guilfoyle, T.J., Reed, J.W. Development (2005) [Pubmed]
  8. MASSUGU2 encodes Aux/IAA19, an auxin-regulated protein that functions together with the transcriptional activator NPH4/ARF7 to regulate differential growth responses of hypocotyl and formation of lateral roots in Arabidopsis thaliana. Tatematsu, K., Kumagai, S., Muto, H., Sato, A., Watahiki, M.K., Harper, R.M., Liscum, E., Yamamoto, K.T. Plant Cell (2004) [Pubmed]
  9. PICKLE is required for SOLITARY-ROOT/IAA14-mediated repression of ARF7 and ARF19 activity during Arabidopsis lateral root initiation. Fukaki, H., Taniguchi, N., Tasaka, M. Plant J. (2006) [Pubmed]
  10. ARF7 and ARF19 regulate lateral root formation via direct activation of LBD/ASL genes in Arabidopsis. Okushima, Y., Fukaki, H., Onoda, M., Theologis, A., Tasaka, M. Plant. Cell (2007) [Pubmed]
  11. The NPH4 locus encodes the auxin response factor ARF7, a conditional regulator of differential growth in aerial Arabidopsis tissue. Harper, R.M., Stowe-Evans, E.L., Luesse, D.R., Muto, H., Tatematsu, K., Watahiki, M.K., Yamamoto, K., Liscum, E. Plant Cell (2000) [Pubmed]
  12. Mutations of Arabidopsis in potential transduction and response components of the phototropic signaling pathway. Liscum, E., Briggs, W.R. Plant Physiol. (1996) [Pubmed]
  13. Overlapping and non-redundant functions of the Arabidopsis auxin response factors MONOPTEROS and NONPHOTOTROPIC HYPOCOTYL 4. Hardtke, C.S., Ckurshumova, W., Vidaurre, D.P., Singh, S.A., Stamatiou, G., Tiwari, S.B., Hagen, G., Guilfoyle, T.J., Berleth, T. Development (2004) [Pubmed]
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