Schematic diagram of AtEF1α-A3 5'UTR intron deletion series. A series of truncated EF1α-A3 5'UTR introns from AT1G07940 were generated. Fifty nucleotides up and downstream of the intron acceptor and donor sites were maintained for splicing efficiency. The deletions are grouped according to the position of the deletion point relative to the 3' region of the intron. Normalised relative luciferase values represent the regression of six independent measurements (see also Figure 9).