A combinatorial role for exon, intron and splice site sequences in splicing in maize |
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Authors: | Jose C Carle-Urioste Volker Brendel Virginia Walbot |
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Institution: | Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA;Department of Mathematics, Stanford University, Stanford, CA 94305-5020, USA |
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Abstract: | Plant introns are typically AU-rich or U-rich, and this feature has been shown to be important for splicing. In maize, however, about 20% of the introns exceed 50% GC, and most of them are efficiently spliced. A series of constructs has been designed to analyze the cis requirements for splicing of the GC-rich Bz2 maize intron and two other GC-rich intron derivatives. By manipulating exon, intron and splice site sequences it is shown that exons can play an important role in intron definition: changes in exon sequences can increase splicing efficiency of a GC-rich intron from 17% to 86%. The relative difference, or base compositional contrast, in GC and U content between exon and intron sequences in the vicinity of splice sites, rather than the absolute base-content of the intron or exons, correlates with splicing efficiency. It is also shown that GC-rich intron constructs that are poorly spliced can be partially rescued by an improved 3' splice site. |
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