A combinatorial role for exon, intron and splice site sequences in splicing in maize

Area of Science:

• Molecular Biology
• Plant Genetics
• Gene Splicing Mechanisms

Background:

• Plant introns are typically AU-rich, crucial for splicing.
• Maize presents exceptions with ~20% GC-rich introns, yet efficiently spliced.
• Understanding GC-rich intron splicing in maize is vital.

Purpose of the Study:

• To investigate cis requirements for splicing GC-rich maize introns.
• To analyze the role of exon and intron sequences in splicing efficiency.
• To determine factors influencing the splicing of GC-rich Bz2 maize intron.

Main Methods:

• Designed and analyzed constructs of GC-rich maize introns (Bz2 and derivatives).
• Manipulated exon, intron, and splice site sequences to assess splicing efficiency.
• Correlated base composition (GC and U content) with splicing outcomes.

Main Results:

• Exon sequence manipulation significantly enhanced GC-rich intron splicing efficiency (17% to 86%).
• Splicing efficiency correlates with base compositional contrast between exons and introns near splice sites.
• Improved 3' splice sites partially rescued poorly spliced GC-rich intron constructs.

Conclusions:

• Exons play a critical role in defining GC-rich introns for splicing in maize.
• Base compositional contrast, not absolute GC content, is key for efficient splicing.
• Splice site optimization can improve splicing of recalcitrant GC-rich introns.