Relationship between 5′ UTR length and gene expression pattern in chicken

The chicken (Gallus gallus) is an important model organism that bridges the evolutionary gap between mammals and non-amniote vertebrates. Here, we carried out a systematic study of the relationship between 5' UTR length and gene expression pattern in the chicken genome. We found that gene 5' UTRs lengths show a negative correlation with gene expression levels and gene expression breadths significantly. The relevance of 5' UTR length to expression pattern can not be a consequence of transcription-associated mutations. We also found that gene 5' UTR length shows a weakly positive correlation with gene tissue specificity. Another intriguing finding is that genes with 5' UTR length < 30 bp have highest expression level, highest expression breadth, and lowest tissue specificity in chicken. We argued that selection is likely involved in shaping 5' UTR length in the chicken genome.