Differences in intron-mediated enhancement of gene expression by the first intron of cytosolic superoxide dismutase gene from rice in monocot and dicot plants

Abstract

Introns have an enhancing effect on gene expression known as intron-mediated enhancement in various organisms, including plants. Although the mechanism of the enhancement is largely unknown, most enhancing introns are first introns. In this study, we examined whether the first intron of rice superoxide dismutase sodCc2 gene has an enhancing effect in rice and other plant species. A transient expression assay revealed that the sodCc2 intron elevated reporter gene expression in rice, wheat, and maize, but not in Arabidopsis and tobacco, indicating that the sodCc2 intron has an enhancing effect in monocot but not in dicot plants. To find the putative signal sequences responsible for the enhancement, we carried out an in silico search and found two motifs conserved among the sodCc2 intron and 11 enhancing introns previously known in rice. The motifs contain a consensus sequence, GATCTG, which also exists in the conserved motif found in Arabidopsis enhancing introns. Our results suggest that common motifs are conserved between rice and Arabidopsis enhancing introns.