Dhadi Surendar Reddy, Xu Zijun, Shaik Rafi, Driscoll Kyle, Ramakrishna Wusirika
Department of Biological Sciences, Michigan Technological University, Houghton, MI, 49931, USA.
Plant Mol Biol. 2015 Apr;87(6):603-13. doi: 10.1007/s11103-015-0300-7. Epub 2015 Feb 20.
Rice genome harbors genes and promoters with retrotransposon insertions. There is very little information about their function. The effect of retrotransposon insertions in four rice promoter regions on gene regulation, was investigated using promoter-reporter gene constructs with and without retrotransposons. Differences in expression levels of gus and egfp reporter genes in forward orientation and rfp in reverse orientation were evaluated in rice plants with transient expression employing quantitative RT-PCR analysis, histochemical GUS staining, and eGFP and RFP fluorescent microscopy. The presence of SINE in the promoter 1 (P1) resulted in higher expression levels of the reporter genes, whereas the presence of LINE in P2 or gypsy LTR retrotransposon in P3 reduced expression of the reporter genes. Furthermore, the SINE in P1 acts as an enhancer in contrast with the LINE in P2 and the gypsy LTR retrotransposon in P3 which act as silencers. CTAA and CGG motifs in these retrotransposons are the likely candidates for the downregulation compared to TCTT motif (SINE) which is a candidate for the upregulation of gene expression. The effect of retrotransposons on gene regulation correlated with the earlier investigation of conservation patterns of these four retrotransposon insertions in several rice accessions implying their evolutionary significance.
水稻基因组含有带有逆转座子插入的基因和启动子。关于它们的功能，信息非常少。使用带有和不带有逆转座子的启动子-报告基因构建体，研究了四个水稻启动子区域中逆转座子插入对基因调控的影响。通过定量RT-PCR分析、组织化学GUS染色以及eGFP和RFP荧光显微镜观察，在瞬时表达的水稻植株中评估了正向gus和egfp报告基因以及反向rfp报告基因表达水平的差异。启动子1（P1）中SINE的存在导致报告基因的表达水平更高，而P2中的LINE或P3中的吉普赛LTR逆转座子的存在则降低了报告基因的表达。此外，与P2中的LINE和P3中的吉普赛LTR逆转座子作为沉默子相反，P1中的SINE起到增强子的作用。与作为基因表达上调候选序列的TCTT基序（SINE）相比，这些逆转座子中的CTAA和CGG基序可能是下调的候选序列。逆转座子对基因调控的影响与先前对这四个逆转座子插入在几个水稻品种中的保守模式的研究相关，这暗示了它们的进化意义。
