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Antifreeze proteins in winter rye leaves form oligomeric complexes
Plant Physiology
|April 10, 1999
Summary
Winter rye antifreeze proteins (AFPs) form complex structures in leaves during cold acclimation. These oligomeric complexes, containing glucanase-like, chitinase-like, and thaumatin-like proteins, are more effective at inhibiting ice growth.
Area of Science:
- Plant physiology
- Molecular biology
- Cryobiology
Background:
- Antifreeze proteins (AFPs) in winter rye (Secale cereale) leaves are crucial for modifying ice growth during freezing.
- These AFPs are similar to pathogenesis-related proteins, including glucanase-like protein (GLP), chitinase-like protein (CLP), and thaumatin-like protein (TLP).
Purpose of the Study:
- To characterize the native forms of winter rye AFPs.
- To investigate the in vivo structure and function of these antifreeze proteins.
Main Methods:
- Native-polyacrylamide gel electrophoresis (PAGE) to separate proteins in their native state.
- Sodium dodecyl sulfate-PAGE to analyze polypeptide composition after denaturation.
- Immunoblotting and antiserum precipitation to identify protein components and interactions.
Main Results:
- Nine distinct proteins were identified in apoplastic extracts of cold-acclimated winter rye leaves.
- Seven of these proteins comprised multiple polypeptides, indicating complex formation.
- Immunoblotting revealed combinations of GLP, CLP, and TLP within isolated proteins, alongside other unidentified proteins.
- Antisera against GLP, CLP, and TLP inhibited glucanase activity and precipitated all three proteins, suggesting surface exposure of these components.
Conclusions:
- Winter rye AFPs exist as oligomeric complexes in vivo.
- These complexes may enhance ice-binding capacity through larger surface area or increased protein mass.
- AFP oligomerization likely increases their efficacy in inhibiting ice growth and recrystallization compared to individual polypeptides.
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