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The regulation of DWARF4 expression is likely a critical mechanism in maintaining the homeostasis of bioactive brassinosteroids in Arabidopsis.
- Source :
-
Plant physiology [Plant Physiol] 2006 Feb; Vol. 140 (2), pp. 548-57. Date of Electronic Publication: 2006 Jan 11. - Publication Year :
- 2006
-
Abstract
- Mutants that are defective in brassinosteroid (BR) biosynthesis or signaling display severely retarded growth patterns due to absence of growth-promoting effects by BRs. Arabidopsis (Arabidopsis thaliana) DWARF4 (DWF4) catalyzes a flux-determining step in the BR biosynthetic pathways. Thus, it is hypothesized that the tissues of DWF4 expression may represent the sites of BR biosynthesis in Arabidopsis. Here we show that DWF4 transcripts accumulate in the actively growing tissues, such as root, shoot apices with floral clusters, joint tissues of root and shoot, and dark-grown seedlings. Conforming to the RNA gel-blot analysis, DWF4:beta-glucuronidase (GUS) histochemical analyses more precisely define the tissues that express the DWF4 gene. Examination of the endogenous levels of BRs in six and seven different tissues of wild type and brassinosteroid insensitive1-5 mutant, respectively, revealed that BRs are significantly enriched in roots, shoot tips, and joint tissues of roots and shoots. In addition, DWF4:GUS expression was negatively regulated by BRs. DWF4:GUS activity was increased by treatment with brassinazole, a BR biosynthetic inhibitor, and decreased by exogenous application of bioactive BRs. When DWF4:GUS was expressed in a different genetic background, its level was down-regulated in brassinazole resistant1-D, confirming that BRASSINAZOLE RESISTANT1 acts as a negative regulator of DWF4. Interestingly, in the brassinosteroid insensitive2/dwf12-1D background, DWF4:GUS expression was intensified and delocalized to elongating zones of root, suggesting that BRASSINOSTEROID INSENSITIVE2 is an important factor that limits DWF4 expression. Thus, it is likely that the DWF4 promoter serves as a focal point in maintaining homeostasis of endogenous bioactive BR pools in specific tissues of Arabidopsis.
- Subjects :
- Arabidopsis growth & development
Arabidopsis metabolism
Arabidopsis Proteins analysis
Arabidopsis Proteins metabolism
Cytochrome P-450 Enzyme System analysis
Cytochrome P-450 Enzyme System metabolism
Endoplasmic Reticulum metabolism
Flowers anatomy & histology
Flowers metabolism
Homeostasis
Light
Molecular Sequence Data
Plant Roots anatomy & histology
Plant Roots metabolism
Plant Shoots anatomy & histology
Plant Shoots metabolism
Protoplasts cytology
Protoplasts metabolism
RNA, Plant metabolism
Recombinant Fusion Proteins metabolism
Reverse Transcriptase Polymerase Chain Reaction
Seedlings anatomy & histology
Seedlings metabolism
Steroid Hydroxylases genetics
Steroid Hydroxylases metabolism
Steroids metabolism
Arabidopsis genetics
Arabidopsis Proteins genetics
Cytochrome P-450 Enzyme System genetics
Gene Expression Regulation, Plant
Plant Growth Regulators biosynthesis
Subjects
Details
- Language :
- English
- ISSN :
- 0032-0889
- Volume :
- 140
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Plant physiology
- Publication Type :
- Academic Journal
- Accession number :
- 16407451
- Full Text :
- https://doi.org/10.1104/pp.105.067918