In order to test whether functional complexity of tissue-specific expression has produced both large introns and large proteins in tissue-specific genes, we compared genes' intron length with similar expression levels but differing greatly in expression breadth (ubiquitously expressed genes and narrowly expressed genes with similar expression levels).
To test whether functional complexity of tissue-specific expression has produced both large introns and large proteins in tissue-specific genes [ 32], we compared genes with similar expression levels but differing greatly in expression breadth (ubiquitously expressed genes and narrowly expressed genes with similar expression levels).
Ubiquitously expressed genes have much higher germline expression level than narrowly expressed somatic genes with the consideration of ectopical expression[ 18].
We found that housekeeping genes are not more compact than narrowly expressed genes with similar expression levels, but compactness and expression level are correlated in housekeeping genes (except that highly expressed Arabidopsis HK genes have longer intron length).
Because housekeeping genes are expected to have much higher germline expression levels than narrowly expressed somatic genes, transcription-associated deletion bias is not supported.
The sentence "Comparison analyses showed that ubiquitously expressed genes are less compact than narrowly expressed genes with similar expression levels (P = 0.2386)" has been corrected to "Comparison analyses showed that ubiquitously expressed genes and narrowly expressed genes with the similar expression levels do not differ in compactness (P = 0.2386)".
For instance, in the initial draft of the manuscript the authors suggested that "ubiquitously expressed genes are less compact than narrowly expressed genes with similar expression levels (P = 0.2386)".
Zhang et al analyzed the results of UniGene clusters [ 16] and pointed out that most narrowly expressed transcripts (NETs), whose expression is confined to a few tissues, resemble intergenic sequences, and most NETs are singleton clusters containing only one EST or mRNA sequence.
We also compared ubiquitously expressed genes and narrowly expressed somatic genes with similar expression levels.
However, by comparing artificially selected pairs of housekeeping and narrowly expressed genes with similar average expression levels, Li et al. [ 6] recently found that housekeeping genes are no more compact than narrowly expressed genes if the expression level is controlled.
Our data demonstrated that ubiquitously expressed genes are less compact than narrowly expressed genes with the similar expression levels.
