The effects of a stimulating intron on the expression of heterologous genes in A rabidopsis thaliana

Introns are often added to transgenes to increase expression, although the mechanism through which introns stimulate gene expression in plants and other eukaryotes remains mysterious. While introns vary in their effect on expression, it is unknown whether different genes respond similarly to the same stimulatory intron. Furthermore, the degree to which gene regulation is preserved when expression is increased by an intron has not been thoroughly investigated. To test the effects of the same intron on the expression of a range of genes, GUS translational fusions were constructed using the promoters of eight Arabidopsis genes whose expression was reported to be constitutive ( GAE 1, CNGC 2 and ROP 10 ), tissue specific ( ADL 1A, YAB 3 and At AMT 2 ) or regulated by light ( ULI 3 and MSBP 1 ). For each gene, a fusion containing the first intron from the UBQ 10 gene was compared to fusions containing the gene's endogenous first intron (if the gene has one) or no intron. In every case, the UBQ 10 intron increased expression relative to the intronless control, although the magnitude of the change and the level of expression varied. The UBQ 10 intron also changed the expression patterns of the CNGC 2 and YAB 3 fusions to include strong activity in roots, indicating that tissue specificity was disrupted by this intron. In contrast, the regulation of the ULI 3 and MSBP 1 genes by light was preserved when their expression was stimulated by the intron. These findings have important implications for biotechnology applications in which a high level of transgene expression in only certain tissues is desired.