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Expansin-like molecules: novel functions derived from common domains
N N Ludidi1, J L Heazlewood, C Seoighe
1Department of Biochemistry, University of the Western Cape, Private Bag X17, Bellville, 7535, South Africa.
Journal of Molecular Evolution
|April 20, 2002
Summary
Plant natriuretic peptide analogs (irPNPs) in Arabidopsis thaliana are related to expansins and evolved from glucanases. These novel proteins interact with the plasma membrane, suggesting a role in systemic water and solute homeostasis.
Area of Science:
- Plant Molecular Biology
- Evolutionary Biology
- Biochemistry
Background:
- Arabidopsis thaliana transcript AtPNP-A encodes an immunoreactant plant natriuretic peptide (irPNP) analog.
- The irPNP analog shows similarity to citrus protein CjBAp12, which is induced by blight infection and related to expansins but lacks cell wall loosening activity.
Purpose of the Study:
- To investigate the evolutionary and functional relationships of irPNP-like molecules.
- To understand their place within the expansin superfamily and related protein families.
Main Methods:
- Sequence analysis to identify evolutionary relationships.
- Comparison of conserved motifs and domain structures.
- Functional assays using protoplasts and microsomes.
Main Results:
- irPNP-like molecules are related to expansins, forming two groups: CjBAp12 and AtPNP-A.
- Shared motifs (K[VI]VD, [LM]SxxAFxxI) were identified, but the typical expansin C-terminal domain is absent.
- irPNPs interact with the plasma membrane, not requiring cell walls for activity.
Conclusions:
- irPNP-like molecules and expansins likely evolved from ancestral glucanase-like enzymes.
- The absence of a cell wall-binding domain and plasma membrane interaction suggest a systemic role for irPNPs.
- These proteins are implicated in regulating water and solute homeostasis in plants.