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Expression and processing of a hormonally regulated beta-expansin from soybean
B P Downes1, C R Steinbaker, D N Crowell
1Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, Indiana 46202-5132, USA.
Plant Physiology
|May 15, 2001
Summary
Soybean beta-expansin Cim1 is induced by cytokinin and auxin, undergoing post-translational modifications like N-glycosylation and proteolysis. These changes are linked to soybean growth and cell wall loosening.
Area of Science:
- Plant molecular biology
- Biochemistry
- Cell biology
Background:
- Expansin proteins facilitate acid-induced plant cell wall loosening.
- Beta-expansins, a subfamily, include grass pollen allergens.
- Understanding beta-expansin expression is crucial for plant growth studies.
Purpose of the Study:
- Characterize the cytokinin-inducible beta-expansin Cim1 from soybean (Glycine max).
- Investigate the synergistic effects of cytokinin and auxin on Cim1 expression and processing.
- Elucidate the post-translational modifications of Cim1.
Main Methods:
- Hormonal induction assays in cultured soybean cells.
- Analysis of protein accumulation and processing using biochemical techniques.
- Identification of protein modifications including N-glycosylation and proteolysis.
Main Results:
- Cytokinin and auxin synergistically induce Cim1 accumulation and processing.
- Cim1 undergoes carboxyl-terminal truncation, yielding 35-kD and 20-kD forms.
- A propeptide fragment is N-glycosylated via a tunicamycin-sensitive pathway.
- Cim1 expression correlates with increased soybean culture growth.
- Cim1 is rapidly proteolyzed as cultures reach stationary phase.
Conclusions:
- Beta-expansin Cim1 is subject to significant post-translational modifications.
- N-glycosylation and proteolysis are key regulatory mechanisms for Cim1 function.
- These modifications are linked to soybean growth dynamics and cell wall loosening processes.