Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

Expression of gibberellin 20-oxidase1 (AtGA20ox1) in Arabidopsis seedlings with altered auxin status is regulated at multiple levels

Isabel Desgagné-Penix and Valerie M. Sponsel
Journal of Experimental Botany
Vol. 59, No. 8 (2008), pp. 2057-2070
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/24037559
Page Count: 14
  • Download ($42.00)
  • Cite this Item
Expression of gibberellin 20-oxidase1 (AtGA20ox1) in Arabidopsis seedlings with altered auxin status is regulated at multiple levels
Preview not available

Abstract

Bioactive gibberellins (GAs) affect many biological processes including germination, stem growth, transition to flowering, and fruit development. The location, timing, and level of bioactive GA are finely tuned to ensure that optimal growth and development occur. The balance between GA biosynthesis and deactivation is controlled by external factors such as light and by internal factors that include auxin. The role of auxin transport inhibitors (ATIs) and auxins on GA homeostasis in intact light-grown Arabidopsis thaliana (L.) Heynh. seedlings was investigated. Two ATIs, 1-N-naphthylthalamic acid (NPA) and 1-naphthoxyacetic acid (NOA) caused elevated expression of the GA biosynthetic enzyme AtGA20-oxidase1 (AtGA20ox1) in shoot but not in root tissues, and only at certain developmental stages. It was investigated whether enhanced AtGA20ox1 gene expression was a consequence of altered flow through the GA biosynthetic pathway, or was due to impaired GA signalling that can lead to enhanced AtGA20ox1 expression and accumulation of a DELLA protein, Repressor of ga1-3 (RGA). Both ATIs promoted accumulation of GFP-fused RGA in shoots and roots, and this increase was counteracted by the application of GA4. These results suggest that in ATI-treated seedlings the impediment to DELLA protein degradation may be a deficiency of bioactive GA at sites of GA response. It is proposed that the four different levels of AtGA20ox1 regulation observed here are imposed in a strict hierarchy: spatial (organ-, tissue-, cell-specific) > developmental > metabolic > auxin regulation. Thus results show that, in intact auxin- and auxin transport inhibitor-treated light-grown Arabidopsis seedlings, three other levels of regulation supersede the effects of auxin on AtGA20ox1.

Page Thumbnails

  • Thumbnail: Page 
[2057]
    [2057]
  • Thumbnail: Page 
2058
    2058
  • Thumbnail: Page 
2059
    2059
  • Thumbnail: Page 
2060
    2060
  • Thumbnail: Page 
2061
    2061
  • Thumbnail: Page 
2062
    2062
  • Thumbnail: Page 
2063
    2063
  • Thumbnail: Page 
2064
    2064
  • Thumbnail: Page 
2065
    2065
  • Thumbnail: Page 
2066
    2066
  • Thumbnail: Page 
2067
    2067
  • Thumbnail: Page 
2068
    2068
  • Thumbnail: Page 
2069
    2069
  • Thumbnail: Page 
2070
    2070