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Characterization of dull1, a maize gene coding for a novel starch synthase
1Department of Biochemistry and Biophysics, Iowa State University, Ames, Iowa 50011, USA.
The Plant Cell
|April 18, 1998
Summary
The maize dull1 gene regulates starch structure by encoding a starch synthase, likely SSII. Mutations in dull1 primarily impact this enzyme, with secondary effects on other starch-related enzymes.
Area of Science:
- Plant Biology
- Molecular Genetics
- Biochemistry
Background:
- The maize dull1 (du1) gene influences endosperm starch structure.
- Mutations in du1 affect starch synthase II (SSII) and starch branching enzyme IIa (SBEIIa) activity.
Purpose of the Study:
- To identify and characterize novel du1 mutations.
- To clone the du1 locus and determine the Du1 gene sequence.
- To elucidate the function of the Du1 gene product in maize starch biosynthesis.
Main Methods:
- Generation and identification of novel du1 mutations in Mutator-active maize plants.
- Transposon tagging to clone a portion of the du1 locus.
- cDNA sequencing to determine the full-length Du1 sequence.
- Analysis of Du1 gene expression patterns via transcript detection.
Main Results:
- Six novel du1 mutations were identified.
- A nearly full-length Du1 cDNA sequence was obtained, revealing a predicted 1674-residue protein.
- Du1 transcripts were detected in endosperm during starch biosynthesis but not in leaves or roots.
- The Du1 protein shares similarity with potato SSIII and contains unique regions, including a conserved segment found in SBEs.
Conclusions:
- The Du1 gene product is a starch synthase, most likely SSII.
- Secondary effects of du1 mutations, such as reduced SBEIIa activity, are likely a consequence of the primary deficiency in starch synthase II.