Lu Jianli, Sivamani Elumalai, Azhakanandam Kasi, Samadder Partha, Li Xianggan, Qu Rongda
Department of Crop Science, North Carolina State University, Raleigh, NC 27695, USA.
Mol Genet Genomics. 2008 Jun;279(6):563-72. doi: 10.1007/s00438-008-0333-6. Epub 2008 Mar 5.
Introns are important sequence elements that modulate the expression of genes. Using the GUS reporter gene driven by the promoter of the rice (Oryza sativa L.) polyubiquitin rubi3 gene, we investigated the effects of the 5' UTR intron of the rubi3 gene and the 5' terminal 27 bp of the rubi3 coding sequence on gene expression in stably transformed rice plants. While the intron enhanced GUS gene expression, the 27-bp fused to the GUS coding sequence further augmented GUS expression level, with both varying among different tissues. The intron elevated GUS gene expression mainly at mRNA accumulation level, but also stimulated enhancement at translational level. The enhancement on mRNA accumulation, as determined by realtime quantitative RT-PCR, varied remarkably with tissue type. The augmentation by the intron at translational level also differed by tissue type, but to a lesser extent. On the other hand, the 27-bp fusion further boosted GUS protein yield without affecting mRNA accumulation level, indicating stimulation at translation level, which was also affected by tissue type. The research revealed substantial variation in the magnitudes of intron-mediated enhancement of gene expression (IME) among tissues in rice plants and the importance of using transgenic plants for IME studies.
内含子是调节基因表达的重要序列元件。利用由水稻（Oryza sativa L.）多聚泛素rubi3基因启动子驱动的GUS报告基因，我们研究了rubi3基因的5'UTR内含子和rubi3编码序列的5'末端27bp对稳定转化水稻植株中基因表达的影响。虽然内含子增强了GUS基因表达，但与GUS编码序列融合的27bp进一步提高了GUS表达水平，两者在不同组织中均有所不同。内含子主要在mRNA积累水平提高GUS基因表达，但也在翻译水平促进增强。通过实时定量RT-PCR测定，内含子对mRNA积累的增强在不同组织类型中差异显著。内含子在翻译水平的增强也因组织类型而异，但程度较小。另一方面，27bp融合进一步提高了GUS蛋白产量，而不影响mRNA积累水平，表明在翻译水平受到刺激，这也受组织类型的影响。该研究揭示了水稻植株不同组织中内含子介导的基因表达增强（IME）程度存在显著差异，以及使用转基因植物进行IME研究的重要性。
