A comparative computational analysis of nonautonomous helitron elements between maize and rice.

Area of Science:

• Genomics
• Molecular Biology
• Evolutionary Biology

Background:

• Helitrons are DNA transposable elements replicating via a rolling circle mechanism.
• Non-autonomous helitrons in maize capture gene fragments from numerous genes, unlike those in Arabidopsis.
• This suggests divergent evolutionary histories for helitrons in different plant species.

Purpose of the Study:

• To computationally identify helitrons in maize and rice genomes.
• To compare helitron characteristics, including gene capture and diversity, between maize and rice.
• To investigate sequence properties potentially influencing gene capture rates.

Main Methods:

• Computational searches using known helitrons as seed sets.
• Analysis of helitron distribution, polymorphism, and gene fragment capture.
• Examination of 3' palindrome sequence properties and predicted folding energy.

Main Results:

• Identified 23 helitrons in maize, with 5 polymorphic, capturing fragments from 44 genes.
• Discovered over 552 helitrons in japonica rice, with 508 forming a single subfamily.
• Rice helitrons captured fragments from only 11 genes; maize helitrons showed significant diversity, unlike rice.
• Maize helitrons had lower 3' palindrome folding energy than rice, contrary to predictions.

Conclusions:

• Maize helitrons exhibit unique gene capture prevalence compared to rice and Arabidopsis.
• The underlying reasons for differential gene capture remain elusive.
• Evidence for 3' hairpin involvement in transposition termination was minimal.