Complex selection on intron size in Cryptococcus neoformans.

Mol Biol Evol
Authors
Keywords
Abstract

We conducted a genome-wide analysis of the roles of mutation and selection in sculpting intron size in the fungal pathogen Cryptococcus neoformans. We find that deletion rate is positively associated with intron length and that insertion rate exhibits a weak negative association with intron length. These patterns suggest that long introns as well as extremely short introns in this unusually intron-rich fungal genome are in mutation-selection disequilibrium and that the proportion of constrained functional sequence in introns does not scale linearly with size. We find that untranslated region introns are longer than coding-region introns and that first introns are substantially longer than subsequent introns, suggesting heterogeneous distribution of constrained functional sequence and/or selective pressures on intron size within genes. In contrast to Drosophila, we find a positive correlation between d(N) and first intron or last intron length and a negative correlation between d(N) and internal intron length. This contrasting pattern may indicate that terminal introns and internal introns are differentially subject to hypothesized selection pressures modulating intron size and provides further evidence of widespread selective constraints on noncoding sequences.

Year of Publication
2008
Journal
Mol Biol Evol
Volume
25
Issue
2
Pages
247-53
Date Published
2008 Feb
ISSN
1537-1719
URL
DOI
10.1093/molbev/msm220
PubMed ID
18171915
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