Ectopic Expression of a Maize Gene Is Induced by Composite Insertions Generated Through Alternative Transposition

Area of Science:

• Genetics and Genomics
• Molecular Biology
• Plant Science

Background:

• Transposable elements (TEs) are mobile DNA sequences influencing eukaryotic genomes.
• In plants, TEs affect gene expression via insertion, promoter provision, and epigenetic modifications.
• Ac/fAc elements, a class II hAT family, exhibit standard and alternative transposition.

Purpose of the Study:

• To investigate the role of Ac/fAc transposable elements in genome rearrangement and gene expression.
• To demonstrate how alternative transposition events generate composite insertions (CIs).
• To analyze the impact of CIs on the expression of the maize pericarp color 2 (p2) gene.

Main Methods:

• Identification and detailed analysis of over 50 composite insertions (CIs) generated by Ac/fAc alternative transposition.
• Characterization of CI sequences, including the presence of transcriptional enhancers.
• Gene expression analysis of the maize p2 gene in relation to CI presence and excision.

Main Results:

• Alternative transposition of Ac/fAc elements generated numerous composite insertions (CIs).
• Analyzed CIs induced ectopic expression of the maize p2 gene.
• CIs contained enhancer sequences from the nearby p1 gene, mediating p2 activation.
• Excision of CIs abolished p2 expression, confirming their regulatory role.

Conclusions:

• Alternative transposition is a source of genome rearrangements and novel regulatory elements.
• Composite insertions generated by Ac/fAc elements can control gene expression by mobilizing enhancers.
• This mechanism provides new insights into how transposable elements shape gene regulation and genome evolution.