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A Gibberellin-Deficient Brassica Mutant-rosette
S B Rood1, D Pearce, P H Williams
1Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada.
Plant Physiology
|February 1, 1989
Summary
A Brassica rapa mutant with inhibited shoot growth has significantly lower gibberellin (GA) levels. Exogenous GA application rescued the mutant
Area of Science:
- Plant genetics and molecular biology
- Plant physiology
- Biochemistry
Background:
- A single-gene mutant, 'rosette' (ros/ros), was identified in Brassica rapa.
- The mutant exhibits inhibited shoot growth, delayed germination, and incomplete floral development compared to normal plants.
Purpose of the Study:
- To investigate the role of gibberellins (GAs) in the growth and development of the Brassica rapa 'rosette' mutant.
- To quantify endogenous GA levels in the mutant and normal plants.
Main Methods:
- Exogenous application of gibberellic acid (GA(3)) to the mutant.
- Quantification of total GA-like substances using the 'Tan-ginbozu' dwarf rice assay.
- Identification and quantification of free GA(1) and GA(3) using gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM).
Main Results:
- Exogenous GA(3) application to the 'rosette' mutant induced rapid flowering, bolting, and seed production.
- The 'rosette' mutant contained approximately one-tenth the level of total GA-like substances compared to normal plants.
- GC-MS-SIM analysis revealed significantly lower endogenous levels of free GA(1) and GA(3) in the 'rosette' mutant compared to the normal B. rapa line.
Conclusions:
- The 'ros' allele in Brassica rapa leads to reduced endogenous gibberellin levels.
- Endogenous gibberellins, specifically GA(1) and GA(3), play a crucial role in regulating germination, flowering, and shoot growth in Brassica.
- The 'rosette' phenotype is a direct consequence of these reduced GA levels.