Characterization of the maize transposable element Ac by internal deletions

Area of Science:

• Molecular Biology
• Plant Genetics
• Transposable Elements

Background:

• The Ac/Ds system is a well-studied model for genetic transposition in plants.
• Understanding the molecular mechanisms of Ac transposition is crucial for gene function studies and crop improvement.

Purpose of the Study:

• To delineate the specific Ac DNA sequences required for its transposition in tobacco.
• To identify the functional domains of the Ac element responsible for transposase activity.

Main Methods:

• Utilized a phenotypic assay based on Ac excision from the NPTII gene, conferring kanamycin resistance.
• Generated and analyzed various deletion mutants of the Ac element in transgenic tobacco.
• Assessed transposition activity in response to a trans-acting Ac transposase source.

Main Results:

• Deletion of the untranslated leader did not impede Ac excision.
• Deletions within the Ac open reading frame (ORF) abolished or reduced transposition, indicating essential coding sequences.
• Specific deletions (bp 44-92 and bp 75-181) impaired the Ac element's response to a trans-provided transposase.
• Expression of the Ac ORF from a cDNA construct restored Ds element excision.

Conclusions:

• The 3.5-kb Ac transcript likely encodes the sole Ac product, the transposase, essential for transposition.
• Specific regions within the Ac ORF are critical for transposase function and/or interaction with the transposon DNA.